- test-drb@ccmp.vtda.org - classiccmp.org

microcode, compilers, and supercomputer architecture

by CLASSICCMP＠trailing-edge.com

>DEC's customer runnable MicroVax stuff was fairly lame though. Generally, if you can boot the diagnostics on a Microvax, you know that the Microvax is OK. Yep, pretty useless, considering that if you can't boot VMS, you can't boot the diagnostics. The PDP-11 based diagnostics were much more flexible. You could load from paper tape if your disk or tape drive system was sick. You didn't need interrupts or even DMA operational to load them, so you could do some basic tests on a box that didn't even have full backplane continuity! Tim.

27 years, 3 months

3
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Classic (computer literacy textbook)

by max82＠surfree.com

I have the teacher's edition of 'Computer Fundamentals with BASIC programming', copyright 1986. It's in the form of pages to be inserted into a binder. Does anyone want this? --Max Eskin (max82(a)surfree.com)

27 years, 3 months

1
0
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Fooling with floppy drives

by rigdonj＠intellistar.net

At 03:37 AM 4/8/99 -0700, Sellam wrote: >On Thu, 8 Apr 1999, Mike Ford wrote: > >> Coincident with all this chatter on floppy drives I have run into a streak >> of uncooperative drives. I happen to be using macs with 3.5" Sony >> mechanisms, but my question is somewhat general. What do you do with floppy >> drives that need repairs? ><...> >> Do any of you fix your floppies? > >Yes. As much as I can at least. The drive electronics are beyond me but >mechanically I can mend most problems. The issue with the Mac drives >usually tends to be the lubricant that gets gooey over time. You must use >an electronic cleaner like Blue Shower or similar to wash away the gooey >lube, then re-lube it with a suitable lubricating element (I don't >know...sewing machine oil?) This usually unsticks the eject mechanism. HP (sony made) floppy drives have the same problem. They stick part way open and don't eject the disk. If you pull the disk out, you WILL rip the top head off of a double sided drive. Never take a disk out or put a disk into a partially open HP floppy drive. Take the drive out and clean the old lube off so that it opens properly. Joe

27 years, 3 months

4
4
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Stan Veits book

by steverob＠hotoffice.com

Received Stan Veits book (from the Ebay auction) last night. Highly recommended. Steve Robertson - <steverob(a)hotoffice.com>

27 years, 3 months

1
0
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Rotting away

by ethan_dicks＠yahoo.com

> On Thu, 25 Mar 1999, KNIGHT G.A wrote: > > > http://www.nwfl.net/haynesdl/requests/games-a-rottin.JPG > > if ever you're wondering if saving computers from the scrap > > heap is the right thing, check out this link. It's rather a > > sorry sight. > Ow! I'm also a bit of a video-game restorer (presently my best example is a fully restored Gorf), but I've done more to help a friend of mine than I have for myself. At one point, my friend needed some AMD 2901's which are used in the 16-bit math co-pro for Battlezone. We had a pile of dead VAX-11/730 boards at work (self-maintained), so I desoldered some 2901's for him and he was so happy to have VAX parts in his video game. (I still have that 11/730; it was the first machine I ever installed UNIX on, Ultrix 1.1; we used it at work for Usenet before the Great Renaming) Every once in a while, I still go to video-game auctions. It is possible to pick up full-sized games for under $100 if you don't want the hottest games. PacMac, Galaga and other classics are still available, but for big bucks. -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

27 years, 3 months

4
3
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OT was [RANTISH Programming Stupidity]

by steverob＠hotoffice.com

> "In programming, it doesn't matter how well it runs or does it's job. The > bottom line is, 'can we sell it to someone?'" Terrible as it seems, that is a cold hard fact. I'm not sure why everyone thinks that MicroSoft's goal is to build good software. Their ONLY goal is to make money! I don't think anyone can dispute their success at doing that. So, how many billionaires has Linux created? Steve Robertson - <steverob(a)hotoffice.com>

27 years, 3 months

2
1
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Mark-8 Computer - Alive and Ticking!

by jlewczyk＠his.com

Late in Februrary I pulled out of a corner of my workshop a box containing my old Mark-8 computer, the one whose construction was the subject of the cover of Radio Electronics magazine in July 1974. I hadn't looked at in over 22 years! Ah, the memories... When I first read the RE issue, I was in no position financially to purchase anything but the plans ($5 and a SASE, IIRC), being a poor college student (of computer science). It was not until the fall of 1976 that I was able to buy an already constructed Mark-8 from someone who was selling it because he was upgrading (buying a newer microcomputer). I don't know who the original owner was, as the computer was bought by a third party for me. It was astounding to me that I owned my own computer! I proceeded to experiment with it for weeks, hand assembling programs and then keying them in through the front panel! But entering the code through the front panel switches got old real quick, and I endevored to design and build an "octal keyboard and display" for it. The original "backplane" made working on any individual board a real problem: you had to "fan out" the boards to get at the inside ones. So I attempted to make a backplane out of 100-pin wire wrap sockets and bolting edge connectors removed from surplus boards onto the edges of the six Mark-8 circuit boards. After all the work of rewiring the boards with their new edge connectors and wiring the backplane, and then building a new octal front panel board, the computer didn't work at all. (Surprise! ;-) After some time trying to debug it with just a VOM, I abandoned the whole project because I did not have access to the tools (triggered 'scope, logic analyzer, etc.) that I realized I would need to reasonably debug it. Of course there were some great new microcomputers available that were faster and easier to use and program. I bought a KIM-1 and never looked back. Until now. So, I have been attempting to restore the Mark-8 to as close to original condition as possible, which of course includes making it work! ;-). I am pleased to announce that I've been successfull and I'm again the proud owner of a working, .5MHZ computing colossus! I've removed the attempt at a "backplane" and restored it to as close as possible to the origional condition. Originally the computer came with 1K ram, composed of 32 * 256 bit sram chips (Intel 1101A and equivilents). I was dissapointed when I noticed that 1 of the ram chips was missing (I believe it failed, and I threw it out and never replaced it). After getting the system to run with a minimum of 256 bytes, I used memory test routines to check out the remaining memories. I found many more failures, which leaves me with 26 working memory chips. I'm trying to locate more 1101A, so that I'll have enough for 1K and a few spare ones too. Anyone out there have any 1101A or equivilent? (256 bit, pmos, 16 pin package +5V, -9V supply). Another problem I had was a missing 8263 chip (Signetics dual 3-to-1 multiplexor) on the input mux board. I cannot remember why that chip was gone, as the computer certainly wouldn't run at all without it. I probably had removed it to test it, then lost it. I've found that the 8263 chip is impossible to find and have subsequently replaced it with some 74XX chips. I didn't have the data sheet, so I deduced its function by examining the circuit. Only later did I realize that it had inverting outputs, requiring a third chip (a 7404) to complete the replacement circuitry. If anybody out there has an 8263 chip, I'd love to install it an get rid of the replacement circuity. During debugging, I found and replaced three other bad chips, all dealing with the "bus" that I had tried to replace. The other problems were a coupld of solder bridges and various broken connections, especially on the "back plane", which gets flexed every time you fan open the boards in order to access components on them. But the bottom line is.. IT WORKS!!!! And I'm having a great time messing with it. Now what? In the short term, I'm installing the Mark-8 in an appropriate enclosure with a modern switching power supply and fan. I plan on adding an EPROM and UART to it. The EPROM will contain a bootstrap routine for performing a memory check and a "monitor" routine allowing upload from the UART. I want the UART and EPROM to be "vintage" parts (like the AY-3-1013 or COM 2052 UARTs, and 1702A EPROMs. Anyone out there capable of burning a 1702A (or two) for me? I also plan on using a cross-assembler or cross-compiler to write routines for the Mark-8. I'm looking for Intel's PL/M cross compiler and cross-assembler for the 8008. Apparently there also was an 8008 similator. Intel has been suprisingly helpful in reproducing old manuals for the 8008, but the source code for these old tools, THOSE are hard to find. All were written in Fortran, and I understand that Gary Kildall wrote the CP/M compiler. I figure that if I can get the sources, I could port them to the PC. Anybody out there have these old software tools? I also heard that there was a BASIC language for the 8008. Any help with that? Anyone out there have a Mark-8? - John Lewczyk - IO Consulting - 401 Queens Row Street - Herndon, Virginia 20170-3131 - jlewczyk(a)his.com

27 years, 3 months

7
8
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Parity (was Re: stepping machanism of Apple Disk ][ drive)

by ethan_dicks＠yahoo.com

> On Thu, 8 Apr 1999, Richard Erlacher wrote: > > > My contempt for Apple begins and ends with their total disregard for the > > value of your data. > > They designed the MAC with no memory parity assuming that you'd not mind > > if your data was corrupted without your knowledge... Multiple studies of memory reliability (DRAM) show that parity memory is more prone to failure than non-parity memory. If you want reliability, you have to go to something like Error Correcting Codes (ECC) like the big boys use. We had 39-bit memory on a 32-bit VAX (11/750) because the extra seven bits let you *detect* two faulty bits and *correct* a single bit failure. The Sun Enterprise servers I babysit have ECC memory - we used to get one or two failures in the machine room per year, but they were logged and corrected without any loss of data. My Alpha board (AXP-133 "no-name" board) uses 72-pin *parity* SIMMs in pairs to implement ECC on a 64-bit memory bit. The problem with parity is that yes, you do know that you had a failure, but now you have 9 bits that might fail, not 8, raising your risk by 12%. DRAM failures are more often total rather than intermittent. A memory test at power-up is a better insurance policy than relying on parity to save your butt. I did have the parity circuit on a PeeCee cough up a lung once... it was even a five-slot original PC (256K on M.B.). We were using it into the 90's because it was merely the terminal for a Northwest Instruments logic/CPU analyzer that we used to check for problems in our MC68000-based serial boards. One day, the PC would not come up. Because everything was socketed and because I owned an IC tester, we got a bottom-of-the-totem-pole tech grunt to pull each chip and test it. It was a faulty 4164. Labor costs: $25. Parts cost: $0.60 for a part we stocked thousands of for one of our older products. I still have the machine. It still works. I wish I had the invoice for that CPU; the company bought it new in 1981, around $5K, I know, but I'd like to know the exact figure. Bottom line: Apple not using parity is not a reason to trash the Mac. How many PCs have parity since we moved to EDO and SDRAM? It's extra cost and extra complexity and extra possibilities for failure. Unless you can correct the failure, it's not mathematically worth the extra expense and reduced reliability. -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

27 years, 3 months

3
2
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Fwd: Unisys system avail

by sinasohn＠ricochet.net

27 years, 3 months

1
0
0 0

Floppy and Hard disc questions....

by arfonrg＠texas.net

I have just gotten an old GRiDCase 1530 running and now I need to rig some things. First the harddisc: 1) The manual says that it uses an IBM AT compatible harddisc. What's the difference between an IBM AT style harddisc and an IDE? Is there anyway to rig an adapter? 2) There's a floppy expansion plug on the back but I do not know the signals needed for a generic floppy. Is there a web page with the pinouts, signal directions and a signal description? Thanks, Arfon ---------------------------------------- Tired of Micro$oft??? Move up to a REAL OS... ######__ __ ____ __ __ _ __ # #####/ / / / / __ | / / / / | |/ /## ####/ / / / / / / / / / / / | /### ###/ /__ / / / / / / / /_/ / / |#### ##/____/ /_/ /_/ /_/ /_____/ /_/|_|#### # ###### ("LINUX" for those of you without fixed-width fonts) ---------------------------------------- Be a Slacker! http://www.slackware.com Slackware Mailing List: http://www.digitalslackers.net/linux/list.html

27 years, 3 months

2
1
0 0

Floppy and Hard disc questions....

by edick＠idcomm.com

see imbedded comments below, please. Dick -----Original Message----- From: Arfon Gryffydd <arfonrg(a)texas.net> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Friday, April 09, 1999 7:59 AM Subject: Floppy and Hard disc questions.... >I have just gotten an old GRiDCase 1530 running and now I need to rig some >things. > >First the harddisc: > >1) The manual says that it uses an IBM AT compatible harddisc. What's the >difference between an IBM AT style harddisc and an IDE? Is there anyway to >rig an adapter? The PC/AT disk drive used the ST-506 interface (20-conductor data cable, 34-conductor control cable) and what was essentially a WD-1002 WAH controller. The IDE interface is, from a software perspective, essentially the same interface as what was used with the WD controller card. The controller hardware has simply been migrated to the drive. Now, EIDE is another bird. It has enhancements which make it less compatible with that old firmware. It's advisable you try your Grid machine with an old disk drive first before you fiddle with the drive adapter hardware. >2) There's a floppy expansion plug on the back but I do not know the >signals needed for a generic floppy. Is there a web page with the pinouts, >signal directions and a signal description? > What you have to find out is what the pinout of that particular connector is. There are lots of sources for standard FDD interface cable pinout. > >Thanks, > >Arfon >---------------------------------------- > Tired of Micro$oft??? > > Move up to a REAL OS... >######__ __ ____ __ __ _ __ # >#####/ / / / / __ | / / / / | |/ /## >####/ / / / / / / / / / / / | /### >###/ /__ / / / / / / / /_/ / / |#### >##/____/ /_/ /_/ /_/ /_____/ /_/|_|#### ># ###### > ("LINUX" for those of you > without fixed-width fonts) >---------------------------------------- >Be a Slacker! http://www.slackware.com > >Slackware Mailing List: >http://www.digitalslackers.net/linux/list.html

27 years, 3 months

1
0
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microcode, compilers, and supercomputer architecture

by hhacker＠home.com

>> The only deliberately non-deterministic development tool I've ever used was >> a Xilinx FPGA fitter. Somehow it seemed reminiscent of the bogosort >> algorithm. > >Don't get me started on the Xilinx tools. Suffice it to say, I spent >enough time undoing the damage that they did to my designs. I hate >computers that think they can design better than I can. They are almost >always wrong ;-) > >-tony > My point, exactly. It is clearly the case that automated mechanisms are inferior to a quality human intelligence. For anyone to think otherwise is to relegate decisions of life to a computer program. As we all know, or should all know, artificial intelligence falls _way_ short of its lofty goals. William R. Buckley

27 years, 3 months

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Parity (was Re: stepping machanism of Apple Disk ][ drive)

by edick＠idcomm.com

Yes, increasing the amount of memory by 1/8 increases the likelihood of failure by 1/8. The inclination to bury one's head and ignore the potential for memory or bus failure comes from the competition for price advantage on the personal computer market, though. The argument I've heard is "if MAC'c can live with it, so can PC's" which may not be true, but appears to be true enough for the typical user. Once such a memory failure is detected, there's nothing you can do about it except endeavor NOT to save the data which may be corrupted and become aware of the problem. I see memory parity errors (most of the PC's here use parity or single bit error correction) about twice a year. Normally it's when a new box is being brought up and memories aren't seated right or something on that order. I don't know what that says about the memory systems of today. It's been a few years, but I always preferred single-bit correction over parity in sizeable memory arrays. I designed one fairly large buffer memory for Honeywell, which had 72-bit-wide memory, 64 MB deep, which was quite a bit for that time (1991) with single bit correction only to have the manager tell me it was not needed. "Whom are we helping with this added expense?" was his position. I pointed out that it would make memory problems a depot or even field repair whereas it would be a return-to-factory otherwise. He insisted, though. The software lead and I agreed we'd base our memory check on parity, which still allowed for isolation of the faulty SIMM. Since this was not a main system memory but just a data buffer, it didn't matter that it ws defective and firmware could rigorously isolate the faulty device. I'm not sure what you're saying about the relative value of the extra bit of memory versus the risk of promulgating a transient error into infinity by recording it as though it were correct, Ethan. You seem to suggest that it would have been better not to have had the 60-cent memory part in place rather than to find and repair it once its failure was detected by parity circuitry. I doubt you believe that, however. It is true that the addition of parity circuitry means that there is an elevated likelihood of failure proportinal to the increased memory size. It is also true that parity checking circuitry requires time to work, and can, itself, fail as well. Increased circuit complexity does increase the statistical probability of failure. ECC circuitry doesn't decrease the probability of memory failure. It does decrease the amount of down-time resulting from it, and it avoids the data loss and down-time associated with single-bit transient failures, which are more common than hard failures. I guess it's like automobile insurance. If you have assets you need to protect, you buy it. If you haven't you don't. My assessment is that Apple started with the assumption that you don't. Dick -----Original Message----- From: Ethan Dicks <ethan_dicks(a)yahoo.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Friday, April 09, 1999 6:10 AM Subject: Parity (was Re: stepping machanism of Apple Disk ][ drive) > > >> On Thu, 8 Apr 1999, Richard Erlacher wrote: >> >> > My contempt for Apple begins and ends with their total disregard for the >> > value of your data. >> > They designed the MAC with no memory parity assuming that you'd not mind >> > if your data was corrupted without your knowledge... > >Multiple studies of memory reliability (DRAM) show that parity memory is >more prone to failure than non-parity memory. If you want reliability, you >have to go to something like Error Correcting Codes (ECC) like the big boys >use. We had 39-bit memory on a 32-bit VAX (11/750) because the extra seven >bits let you *detect* two faulty bits and *correct* a single bit failure. >The Sun Enterprise servers I babysit have ECC memory - we used to get one or >two failures in the machine room per year, but they were logged and corrected >without any loss of data. My Alpha board (AXP-133 "no-name" board) uses 72-pin >*parity* SIMMs in pairs to implement ECC on a 64-bit memory bit. > >The problem with parity is that yes, you do know that you had a failure, but >now you have 9 bits that might fail, not 8, raising your risk by 12%. DRAM >failures are more often total rather than intermittent. A memory test at >power-up is a better insurance policy than relying on parity to save your butt. > >I did have the parity circuit on a PeeCee cough up a lung once... it was even >a five-slot original PC (256K on M.B.). We were using it into the 90's because >it was merely the terminal for a Northwest Instruments logic/CPU analyzer that >we used to check for problems in our MC68000-based serial boards. One day, the >PC would not come up. Because everything was socketed and because I owned an >IC tester, we got a bottom-of-the-totem-pole tech grunt to pull each chip and >test it. It was a faulty 4164. Labor costs: $25. Parts cost: $0.60 for a >part >we stocked thousands of for one of our older products. I still have the >machine. It still works. I wish I had the invoice for that CPU; the company >bought it new in 1981, around $5K, I know, but I'd like to know the exact >figure. > >Bottom line: Apple not using parity is not a reason to trash the Mac. How >many PCs have parity since we moved to EDO and SDRAM? It's extra cost and >extra complexity and extra possibilities for failure. Unless you can correct >the failure, it's not mathematically worth the extra expense and reduced >reliability. > >-ethan > >_________________________________________________________ >Do You Yahoo!? >Get your free @yahoo.com address at http://mail.yahoo.com >

27 years, 3 months

1
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stepping machanism of Apple Disk ][ drive (was Re: Heatkit 51/4 floppies)

by edick＠idcomm.com

Careful, now! He would have played hell trying to interleave memory accesses between an 8080 and the video refresh process, since its various cycle types were so different. It would have been worse YET with a Z-80! The 6502 also allowed him to proceed with his own DOS and his OWN version of BASIC, without which he mightn't have gotten the strangle-hold on the personal-computers-in-business market. It's pretty hard to criticize his choices, however little I liked the result from the standpoint of seeing it as a tool, but his (and his partner's) decisions were definitely vindicated in the marketplace. Dick -----Original Message----- From: Ward D. Griffiths III <gram(a)cnct.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 10:34 PM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 51/4 floppies) >On Thu, 8 Apr 1999 allisonp(a)world.std.com wrote: > >> Actually there are two points. One is track 000 and the other is the >> innermost (for sa400 35-40 tracks later). Only track 000 was sensored >> save for apple didn't use that either. Apple cut the interface to the >> minimim number of wires and signals possible and made up the difference >> with software, rather clever in my mind. > >During the design phase, Woz had more time than money, chips cost money >and software only cost time. Remember that he _wanted_ to use the 8080 >but the 6502 cost only a tenth the price. (Imagine what the Apple >might have been like with a decent CPU from the start). >-- >Ward Griffiths >"the timid die just like the daring; and if you don't take the plunge then >you'll just take the fall" Michael Longcor >

27 years, 3 months

2
1
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Rotting away

by ethan_dicks＠yahoo.com

--- Roger Merchberger <zmerch(a)30below.com> wrote: > Once upon a midnight dreary, Ethan Dicks had spoken clearly: > > >Every once in a while, I still go to video-game auctions. It is possible to > >pick up full-sized games for under $100 if you don't want the hottest games. > >PacMac, Galaga and other classics are still available, but for big bucks. > > Where? I'd like to pick up a video game (over 10 years old -- something > like "Time Pilot" or somesuch, so this *is* on topic... ;-), but where I > live nothing like that is available. As I said, in my area, there is a company that has a rolling road show that auctions off games and ordinary people and companies alike can buy and sell. I no longer have the contact info for the auction company since I haven't been to an auction in long enought that they have dropped me from the mailing list. > Also, is there a web (or other) reference as to what games used which > processors? I think several games used the Moto6809, and if I had my > druthers, I'd get a game based on that processor, as it's my favo[u]ite. I would think that some of the arcade emulation sites would have that info as it pertains directly to what you can emulate. I don't have any sort of list, but I can say that Gorf and Wizard 0f Wor use the Z-80 and many Atari games use the 6502. -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

27 years, 3 months

1
0
0 0

homemade computer for fun and experience...

by CLASSICCMP＠trailing-edge.com

>How one place characters on terminal, give examples of terminal >coding as sent from computer to terminal? > >-outputting characters to screen? Say you want to print the character 'W'. You put the letter 'W' into the accumulator, and tell it to output to the serial port. >-resetting cursor to different places? For a truly portable interface, you use a mix of carriage returns, line feeds, and spaces/tabs to put the cursor where you want. If you know you'll have a VT52 or VT100 or ADM3A or (insert generic type of terminal here) you can send a specific character sequence. If you're going to be eventually turning this machine into a CP/M platform, I heavily recommend that you read the copy of your "CP/M Customization Guide" that shipped with your CP/M distribution. You'll find the terminal output/input routines explicitly coded as an example in that book. >Which CPU is very friendly for creating basic codings to put into >ROM and assembling? Z80? or suitable CPU? Just about anything. The Z80 certainly is a popular and easy-to-interface to choice. -- Tim Shoppa Email: shoppa(a)trailing-edge.com Trailing Edge Technology WWW: http://www.trailing-edge.com/ 7328 Bradley Blvd Voice: 301-767-5917 Bethesda, MD, USA 20817 Fax: 301-767-5927

27 years, 3 months

1
0
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Microsoft is about to arrest me!

by geoffrob＠stmarks.pp.catholic.edu.au

---------- > From: Robert Lund <lundo(a)interport.net> > To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> > Subject: Re: Microsoft is about to arrest me! > Date: Friday, April 09, 1999 1:45 > > Oh, god! Does Lord Gates now even have his own police force?? Nothing would surprise me. > Supreme Court battle ahead of you to get out of MS Jail. I thought MS Jail was Windoze 9x/NT? You get in to it then it locks up? Cheers Geoff Roberts VK5KDR Computer Systems Manager Saint Marks College Port Pirie, South Australia geoffrob(a)stmarks.pp.catholic.edu.au

27 years, 3 months

1
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stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5 1/4 floppies)

by edick＠idcomm.com

The disk drive has a place beyond which its head assembly won't move. If you've ever written FDC code, you know what it sounds like when you try to go beyond the limit. What's more, there's a sensor to tell you when you're at that point, though I doubt Apple used it. It's just as easy to move the heads until you're sure they've gone as far as they can. Once you've done that, what better way could there be than to look for a track and then adjust until the signal is readable? That's how drives of all sorts work today. Of course, they all have some way of establishing where a track ought to be to begin with. Dick -----Original Message----- From: Max Eskin <max82(a)surfree.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, April 07, 1999 8:53 PM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5 1/4 floppies) >On 8 Apr 1999, Eric Smith wrote: >>> These fellows >>> spent a couple of sessions talking about and demonstrating the screwy means >>> by which certain game vendors in the Apple market were "protecting" their >>> wares by altering the timing of the positioning routine, thereby making it >>> possible to write tracks "off the track" by changing the time delay between >>> a known cylinder position and the point at which the specific track was to >>> be written. This made it impossible for someone using the stock timing of >>> the positioning mechanism to read the diskettes so written. > >How does this work? Do you mean that the disk drive has no internal means >of judging whether or not it's on the right track and that this is >determined by the contents of the disk? > > --Max Eskin (max82(a)surfree.com) >

27 years, 3 months

5
4
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Fooling with floppy drives

by SUPRDAVE＠aol.com

In a message dated 08/04/99 15:36:36 Eastern Daylight Time, mikeford(a)netwiz.net writes: << When you say not reading, is it; Fails to spin at all, so all discs are immediately rejected? Doesn't reliably read? My wet cleaning floppy often helps this case. I have a few diagnostic programs, and I think it is TechTool Pro that will do a full drive test, with a 0% to 100% rating that fairly accurately ranks condition of drives. A few of the refurb places sell drives using this rating, with a 90%+ drive fetching a 100% premium over just a working drive. >> well, my mac IIcx had a drive that wouldnot eject disks. the grease had gummed up so i used an aerosol cleaning product and cleaned all that out and used moly grease to fix the stickiness. i also ran a head cleaning disk in the drive for several minutes and amazingly got the drive reading disks again. my IIx will spit disks out ok but refuses to read known good mac formatted floppies. that was cleaned with a head cleaning disk as well but no improvement. unfortunately, the IIx only has one drive instead of two. I recently got a IIci (nice machine!) and it works great, but there seems to be a drive alignment problem. disks formatted on the cx wont always read right on the IIci. seems that i have to use one external floppy between both macs in order to get 800k disks to be read reliably. grrr.

27 years, 3 months

2
1
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homemade computer for fun and experience...

by edick＠idcomm.com

A reasonable example of how to do these things would be available in the IBM PC Technical Reference, since their display boards used the 6845. The scheme is based on the notion of SHARED memory. The processor writes to the video memory, or to the character memory, and the 6845, once initilized, generates the cursor, and scans through memory at the proper rate to effect display of the content. Unfortunately, Motorola unfortunately didn't include a delay stage to allow for translation of ASCII data to video, so an external latch has to be used to delay sync and blanking by a character clock period, which means you might have to accomodate that in your sync timing as well. it means there will be a 1-character period offset between blanking and character video while the graphics will be "right on." -----Original Message----- From: jpero(a)cgocable.net <jpero(a)cgocable.net> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 11:28 PM Subject: Re: homemade computer for fun and experience... >On my homebuilt computer quest....... > >There's two groups: >Built in video and serial i/o to terminal attached concepts. > >Can you explain the process to "init" and operate video chip based >on 6845 chip with own ram ? Possible to use SRAM with it? >Is there CPU specific limitations? > >I have many of them and certainly get put in use on computer. > >And alteratives: > >How one place characters on terminal, give examples of terminal >coding as sent from computer to terminal? > >-outputting characters to screen? >-resetting cursor to different places? > >Which CPU is very friendly for creating basic codings to put into >ROM and assembling? Z80? or suitable CPU? > >Thanks! > >Wizard

27 years, 3 months

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stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5

by edick＠idcomm.com

I think there may be a semantic problem at hand. The single-density (FM) and double-density (MFM) modulation schemes operate on precisely the same density of flux reversals at the media/head boundary. The difference is that the FM imposes a flux reversal between every bit window, while the MFM does not. What this means is that data encoded in MFM can be written to the media at twice the rate as that at which FM is written without taxing the media or read/write channel ordinarily limited to FM. There were some improvements between earlier and later head designs, and media selected for MFM were required to be better because the bits had half as much material in which to be recorded. With MFM, if a clock was missing, which happened half the time a transition was lost, it didn't necessarily make a difference unless the controller happened to be looking for an address mark. So, if your definition of "double density" means twice as many flux reversals per linear inch, well, you're right, I guess, but that's not what the industry meant when the called it double density. I meant the same thing the rest of the folks in the business meant, i.e twice as much data capacity on the same size medium. It's the same with the difference between MFM and RLL hard disk drives. There were a few drives which, as a matter of course, didn't work with RLL encoding. I don't know why this was. I do know that if you use any of a number of translation schemes, of which ANSI GCR is one, you generate a bit stream which, though it uses more than half the channel bandwith to do so, can be recorded at twice the transfer rate as the corresponding NRZ data without allowing excessive accumulation of charge on the heads as would occur if too many ones or zeroes in succession were recorded in NRZ. These schemes don't require the complicated time domain filters and other "neat" circuits commonly used in read/write channels of that time, and provided sufficient densities of transitions to allow clock recovery. The ANSI GCR translates 4 input bits into 5 recorded bits, and recovers them, and ensures that there are enough transitions to allow clock recovery yet no two adjacent cells have transitions. (?) I suppose this is easily achievable with a PROM, and some folks use a state machine to accomplish the same task. I used a prom. It was easy enough to translate 4 bits received at 5 Mb/sec into 10 bits at 8 Mb/sec. A number of code sets have been developed over the years for the purpose of exploiting such "compression" over digitized voice channels, and many other comm channels. Like I said, the Perscis are hangar queens. Like a BMW . . . in the shop a week a month. That's a hyperbole, of course, but it seems that way when you've paid what the things cost back then only to have to pay that much a year again to keep it running. They were fast, though, and hard disks cost a lot more than the Persci drives. Dick -----Original Message----- From: CLASSICCMP(a)trailing-edge.com <CLASSICCMP(a)trailing-edge.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 9:03 PM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5 >>with positioning. They now use voice-coil actuators rather than steppers, >>and therefore can make quite subtle adjustments in head-stack position >>depending on what is read. Back in the early days, that wasn't so. > >Actually, Persci floppy drives in 1976 or so were voice-coil (and quite >a pain to maintain, even then - these days the glue that holds the >optical graticules in place is often failing, and gluing and realigning >from scratch is even harder, even with all the special Persci >realignment jigs and electronic panels.) And a common modification >to these drives (at least for folks like me who specialize in data >recovery) is software-controlled offsets from the normal track positioning, >something that does use the drive's ability to do fine positioning. > >>One interesting thing about the Apple GCR modulation format is that it >>essentially was a "double-density" technique. > >Eric said the same thing, and I disagree with you both. To me (and all >the tech pubs I've read) the density is how many flux transitions you can >do per second (or revolution). GCR is a way of getting more real data with >the same number of flux transitions. Apple GCR drives use single-density >heads and single density data rates, a considerable cost saving factor >in 1977. > >>cost plenty back then. This was at a time when Radio Shack still stayed >>with single-density, and Apple exceeded their capacity easily. > >While using cheap single-density drives! > >-- > Tim Shoppa Email: shoppa(a)trailing-edge.com > Trailing Edge Technology WWW: http://www.trailing-edge.com/ > 7328 Bradley Blvd Voice: 301-767-5917 > Bethesda, MD, USA 20817 Fax: 301-767-5927

27 years, 3 months

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Heatkit 5 1/4 floppies

by edick＠idcomm.com

I don't feel it necessary to defend what was an obvious memory failure. Eric Smith (much younger than I, and an Apple-owner, unlike me at the time, hence more likely to have paid close attention to the discussion because it affected him and his interests) has already pointed out that I must have been suffering from "old-timer's disease" when coughing up the account of those discussions, though I've corroborated the vague recollection with another old-timer who was there at the time as well, but who also was not an Apple-owner at the time. Since the time of these discussions, I've had occasion to purchase, for a pre-defined purpose, several Apple-II's, some of the wreckage of which and one (maybe more) functional unit of which is serving as a doorstop or spacer between shelves, or some such function. I've nonetheless NEVER looked inside an Apple disk drive, nor have I pondered the schematics beyond noticing that there were such things among the paperwork we got with the half-dozen or so of these units. I never even got particularly familiar with them. I'm certainly not an expert on Apple's hardware, software, or anything else about them. I merely was attempting to recount what I seemed to recall about a specific discussion I witnessed. Clearly the passage of some 20+ years has muddled my recollection. As for the tristate multiplexers, that was an error probably influenced by the fact I'd just plugged a half dozen of them in to three S-100 memory boards I'm giving to some guy in Minnesota who offered me something for them, so I populated them with the requisite IC's, including the 'S257's. I just looked back at the emails I've received in the past month, and couldn't find the specific reference to the part in question, but I must have slipped a couple of numbers in the course of replying to the email in which this subject came up. If they are, indeed, '259's, then they are, as you suggest, addressable latches. Now, I'll hapily accept responsibility for having introduced some error into the discussion of this topic. I guess I'm just going soft in the head. . . That's clearly evidenced in the amount of time I've spent on the discussion of Apple products. Dick -----Original Message----- From: Tony Duell <ard(a)p850ug1.demon.co.uk> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 8:48 PM Subject: Re: Heatkit 5 1/4 floppies >> >> Let me qualify this, first of all, with two bits of fact . . . > >I'll also post some facts. Actually, I'm suprised that nobody else has >done what I've just done, and looked at (a) the Disk II circuit diagrams >and (b) an actual Disk II. Neither are particularly rare. > >> (2) - I remember lengthy discussions among those members of the Denver Area >> 6502-Users' Group who were presumably qualified to discuss the intricacies >> of the internals of APPLE's disk I/O routines at a level I neither knew nor >> cared about, beyond the superficial details I gleaned from the several and >> varied sessions discussing that set of details. Now, I attended these >> weekely and typically 4-hour long meetings for several years, and KNOW the >> guys who were hashing out the details of the hardware and software in >> question knew what they were talking about, so I accept that as fact. If >> it wasn't true, no harm done, but I doubt that was the case. These fellows > >If they claimed that the positioner was a normal DC motor and not a >stepper, then I'm afraid they didn't know what they were talking about. > >Every Disk II that I have ever seen (and I've been working on them for >some 20 years or so) has a stepper as the head positioner. The circuits >show this, with a '259 addressable latch on the controller card to >provide the drive signals and a ULN2003 on the 'analog board' to drive >the windings. > >I'll believe that a drive with a DC motor positioner exists when somebody >shows me one in operation, or provides reasonable evidence (schematics, >software to drive it) that it exists. > >> The scheme with the tristate multiplexers came later, I believe, than the > >What tri-state multiplexers? I can't find a tri-state multiplexer in any >part of the Disk II. > >> was among them. Having said that, I would point out that, given a software >> scheme sequenced the stepper, it is just as possible that one could have >> read the diskettes written a half track off by fiddling with the stepping > >Indeed, and that was done for some copy-protection schemes. >Quarter-tracks might be possible as well... > >> sequence. I doubt, however, that Wayne Wall would have allowed the waste of >> several sessions of the meetings he so firmly controlled back in those days, >> if the assumptions presented as fact in those discussions had not been >> verified. >> >> The helical cam I remember didn't have a groove, but rather, a ridge or >> "fence" in the shape of a helix, which was tracked by a small, >> spring-loaded, roller bearing. This worked quite well, but, because of > >The one I have here has a groove. There's a ball bearing in that groove, >with a spring leaf on top of it fixed to the head assembly. As the disk >rotates, the ball bearing tracks along the groove and moves the head. > >-tony >

27 years, 3 months

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Oops!

by yakowenk＠cs.unc.edu

Due to some kind of editing error, the Classic Computer Rescue list has just the last few words of an entry from someone in New Hampshire. The same problem exists in my backup copy as of about a week ago, and there is no such entry at all in the backup from several months ago. (Yes, I know, I should keep this in RCS. I should do a lot of things.) If your hunting grounds are Southern New Hampshire ("about an hour north of Boston"), please take a moment to send me your new entry. I'll try really hard not to mess it up again! That URL again: http://www.cs.unc.edu/~yakowenk/classiccmp/ccrs_list.html Operators are standing by. :-) Thanks, Bill.

27 years, 3 months

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Microsoft is about to arrest me!

by lundo＠interport.net

Oh, god! Does Lord Gates now even have his own police force?? I think their arrest powers would have to be severely limited - though you might have a long Supreme Court battle ahead of you to get out of MS Jail. -- +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + Robert Lund | "So many good ones, and so many bad ones; + + lundo(a)interport.net | that's what you get for trying." + + New York City | Dutch Schultz, last words + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

27 years, 3 months

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Fooling with floppy drives

by edick＠idcomm.com

There are also the "digital" alignment diskettes. These have certain forms of misalignment intentionally written to certain tracks in a certain way. Together with appropriate software, you can ostensibly detect, quantify, and correct (if you know how and feel you can do it) whatever defects it finds. I've read about this but never got around to trying it. I don't know anyone who's tried it, so I can't even ask the relevant questions. Dysan made a whole series of such digital diagnostic diskettes, as they were called, for various types of disk drives. Unfortunately, they were priced such that it was cheaper to buy a new drive than to buy one of these and the software and fix it yourself. IIRC the price would have crossed over at about 50 drives, not counting the labor savings, since I provided that. The analog alignment process is quite straightforward, but not something I want to do again. Moving the heads back and forth, then tightening the screw holding the lead screw/motor in a fixed position only to have to repeat the process because the changing stresses from tightening things down has caused them to move . . . UGH! . . . Dick -----Original Message----- From: Dwight Elvey <elvey(a)hal.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 4:53 PM Subject: RE[2]: Fooling with floppy drives >Steve Robertson <steverob(a)hotoffice.com> wrote: >> >> I've never used the DYSAN alignment disks and would be really interested to >> learn more about them. >> >> How effective are they? >> What other tools do you need? >> How much do they cost? > >Hi > I've used alignment disks. You need an oscilloscope >to use them. You also need to write a low level >driver to keep the system from freaking when doing >the actual alignment check. They record two signals >on the disk that are 1/2 track above and below the >normal track position ( I don't recall what track you >select but as I recall, it is about half way up >the disk ). The two signals are exactly 1 cycle >per revolution of the disk different in frequency. >You look on your oscilloscope at the analog signal >that comes out of the read amplifier and adjust >for what is call a cats-eye pattern. If the track >alignment is right on, you'll have equal height >signals from the first half of the revolution >as the second half ( sync of the index pulse ). > They also include a constant amplitude track. This >is used to look for contact problems of the disk/head. >One another track they usually have several different >frequency tones recorded. These are used to check the >band pass of the drive. > Other than the cats-eye pattern, there is usually little >that you can adjust on a finished drive. The cats-eye >pattern can be used to fine tune the stepper position. >There are usually some slotted screws someplace that allow >slight changes in the rotation of the stepper. One does >have to check the proper operation of the track zero >sensor after this adjustment because there is interaction. > As for price??? I bought the one I have at a surplus >shop for $1. >Dwight >

27 years, 3 months

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bringing up an 8f...

by allisonp＠world.std.com

Well folks, The 8F is now up and basically healthy. The stuck bit was a bad 74L54 that had a stuck input. Shame the replacement I have is a year older than the machine! I ran one program that will execute on a DECMATE but the result is not visible! ;) / TEST PROGRAM FOR pdp-8f / inchworm view with pannel switch set to Acc (8E/F/M) / 0200 *0200 / start address 0200 7200 START, CLA /CLEAR ACC 0201 1211 TAD WORM /PUT WORM CHARACTER IN ACC 0202 7004 MAIN, RAL / PUSH THE WORM LEFT 0203 7000 DELAY, NOP 0204 7000 NOP 0205 2212 ISZ DELCNT /DELAY 4096 (~20MS) INNER 0206 5203 JMP DELAY 0207 5202 JMP MAIN 0210 7402 HLT 0211 0007 WORM, 0017 / FOUR BIT LONG INCH WORM 0212 0000 DELCNT, 0000 / INSIDE LOOP COUNT 0213 $ Next step is to get the terminal interface in and try it aand also verify all of CORE as all I've checked is most of 00200, page 0 and random words. Allison

27 years, 3 months

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Fooling with floppy drives

by steverob＠hotoffice.com

> I recently got a IIci (nice machine!) and it works great, but there seems to be > a drive alignment problem. disks formatted on the cx wont always read right > on the IIci. seems that i have to use one external floppy between both macs > in order to get 800k disks to be read reliably. grrr. > To me, that is the most frustrating problem. I've got drives that only work with certain disks, disks that only work with certain drives, drives that only format certain densities. Grrr... I guess it could be that both components (disk and drive) are slightly out of tolerance. The end result is, I've got a stack of drives and don't really know if they're good or not. I've had some success by just cleaning the slides and positioning mechanisms. The lubricants really attract the dust and will inhibit movement of the heads. I generally like to use alcohol or another common agent to remove the gunk. Blue Rain works great but, is kinda expensive. You have to be careful not to wash all the lubricant out of the servo bushings. Without any lubrication, they can wear out pretty fast. Especially the spindle motors. I generally use a fine machine oil to lubricate the moving parts. You can also use a very thin coat of vasoline. At least it stays where you put it. I've never used the DYSAN alignment disks and would be really interested to learn more about them. How effective are they? What other tools do you need? How much do they cost? Steve Robertson - <steverob(a)hotoffice.com>

27 years, 3 months

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Fooling with floppy drives

by edick＠idcomm.com

I'm with you on this one. I didn't make or wish it so. AlI did was state how things are. There ought to be a way to fix these things, but since their cheaper bretheren are available for the PC (throw-away) market, it's hard to get someone to fix them for less than a new one costs. Keep in mind that a guy who fixes them himself can do the job, but even an altruistic fellow indeed would rather spend $25 to replace a drive than spend half a day only to find he can't fix the $#@!! thing. Many of the drives to which I refer have only a switch, a couple of optical interrupters, and a single IC on board. . . . . . maybe a few resistors . . . . . They're just not made to repair. Now, if you save a few, perhaps a board swap can help, but be careful! Those high-density connectors attaching the FLEX to the board aren't made to be cycled more than once. They break! Dick -----Original Message----- From: Sellam Ismail <dastar(a)ncal.verio.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 1:49 PM Subject: Re: Fooling with floppy drives >On Thu, 8 Apr 1999, Richard Erlacher wrote: > >> Since new floppy drives cost about $25 including shipment, it's difficult to >> justify repairing them. This is frustrating for people like you who have >> drives for which replacements are not readily available for $20 or so. > >What? What if you don't have $25 laying around, or $25 * 12 = $300 as >Mike says is his current number of broken drives. You don't just go and >pull $25 out of your pocket everytime a drive breaks. The last I checked >money still doesn't grow in the pasture (believe me, I check every >morning). > >> Your experience with sloppy workmanship gives clear indication that $10 per >> hour is not enough to pay a competent technician. The occasional look >> inside should give you good indication of why one who can't spend more than >> 15 minutes' time fixing a $20 drive, can't get the job done. These devices >> must be considered "throw-away" items by now. You've got to learn to >> fix-em-yourself. > >Well, exactly. That's why its called a hobby. > >Sellam Alternate e-mail: dastar(a)siconic.com >--------------------------------------------------------------------------- --- >Don't rub the lamp if you don't want the genie to come out. > > Coming in 1999: Vintage Computer Festival 3.0 > See http://www.vintage.org/vcf for details! > [Last web site update: 04/03/99] >

27 years, 3 months

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Request for Assistance: Houston, Texas

by dastar＠ncal.verio.com

Is anywhere here in or near Houston? I need someone to retrieve and ship a rather large set of items (non-computer related) to California for me. I'll make it worth your while of course. Please contact me privately. Thanks! Sellam Alternate e-mail: dastar(a)siconic.com ------------------------------------------------------------------------------ Don't rub the lamp if you don't want the genie to come out. Coming in 1999: Vintage Computer Festival 3.0 See http://www.vintage.org/vcf for details! [Last web site update: 04/03/99]

27 years, 3 months

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2901s was Re: Rotting away

by ethan_dicks＠yahoo.com

--- Joe <rigdonj(a)intellistar.net> wrote: > Ethan, > > Can you give me a list of machines that you know of that have 2901s? I > know 2901s are in short supply. I'll try to find some in those old game > machines. Any of the Atari vector machines are likely to have 2901's as the core of a math co-processor to manupulate those vectors faster than the little 6502 ever could. My friend Tony is the Atari vector king; I've never owned one, unfortunately. -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

27 years, 3 months

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stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5

by edick＠idcomm.com

Let's not confuse things here. Today, most disks use either a servo track on an unused surface or they use embedded servo written right in with the data they're storing. That certainly helps with speed control as well as with positioning. They now use voice-coil actuators rather than steppers, and therefore can make quite subtle adjustments in head-stack position depending on what is read. Back in the early days, that wasn't so. In that sense, it's fair to say that Apple was somewhat forward in their thinking. Normally they only thought inward, hence, they did this because it saved them money. FM, MFM, RLL including GCR, are simply modulation schemes. They characterize how the data is actually written on the track, but really aren't involved in decoding the position when a track is being found. The data format, however, customarily has extensive information allowing the system to verify the current position of the head on the medium. A typical sort of format layout would have a sync field, followed by an address mark (a framing-sync character sort-of like the unique word used in HDLC and other protocols) to tell the controller what's next, then a position indicator data field to tell the system the current head and sector information, then a CRC, followed by another sync field containing a write splice (write turn-on gap) followed by a data address mark followed by the data and its CRC and yet another sync field containing yet another write splice(write turn-off gap). There are variations on this theme, but that's basically what's there. The basic format is written in the "low-level" format process while the data fields are written in the "high-level" format. On old drives, the drive's internals don't care about the data. They just transfer it. Newer drives, since they have to fiddle with the data in order to set the data rate, manipulate the heads, buffer the data, correct the errors, etc. care very much about and involve themselves greatly with the media content. Hence, they rely less on hardware specifically in place to yield position information. Floppy drives, AFAIK, don't bother with this, though the ZIP and LS-120 drives may very well do so. They have a track-zero detector, and, normally, that's what's used by the system to find track-00. Apple didn't even use one of those because they could move the heads until it seemed reasonable for one reason or another to assume track zero had been reached, perhaps by reading where they were and then making an adjustment, or perhaps by moving the head in one direction or the other until it had to be at the limit. Then they could step inward until data was encountered, and could be interpreted. Someone else will have to elucidate on that, however, because although I know a fair amount about what they might have done, I don't actually know what they did. How about it Eric? How dit they manage a recal? One interesting thing about the Apple GCR modulation format is that it essentially was a "double-density" technique. It was cleverly implemented in a way which saved on hardware, capitalized on software's ability to exploit the time window normally spent waiting for a transfer, and, especially, didn't wed them to one or another FDC chip maker. Those IC's cost plenty back then. This was at a time when Radio Shack still stayed with single-density, and Apple exceeded their capacity easily. Radio Shack was the only major competitor Apple had. This was a real coup! Dick -----Original Message----- From: Cameron Kaiser <ckaiser(a)oa.ptloma.edu> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 6:32 PM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5 >::> How does this work? Do you mean that the disk drive has no internal means >::> of judging whether or not it's on the right track and that this is >::> determined by the contents of the disk? >:: >::Basically, yes. The track and sector are stored in the sector header of >::each sector, among other data. > >In fact, most floppy disk systems work that way. Commodore GCR does that. >So does MFM, doesn't it? > >-- >-------------------------- personal page: http://calvin.ptloma.edu/~spectre/ -- >Cameron Kaiser Database Programmer/Administrative Computing >Point Loma Nazarene University Fax: +1 619 849 2581 >ckaiser(a)ptloma.edu Phone: +1 619 849 2539 >-- FORTUNE: You will feel gypped by this fortune. -----------------------------

27 years, 3 months

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Fooling with floppy drives

by mikeford＠netwiz.net

Coincident with all this chatter on floppy drives I have run into a streak of uncooperative drives. I happen to be using macs with 3.5" Sony mechanisms, but my question is somewhat general. What do you do with floppy drives that need repairs? Normally I just put them aside, but after this week I have close to a dozen in the defective box and ZERO (actually a negative number since I need even more) reliable units that aren't already installed in other systems. I have already performed the first aid procedures like cleaning the heads (using a wet cleaning floppy), and disassembly down to the bare mechanism and blowing out the bunnies with canned air. This pile is the hard core rejects, floppy doesn't spin, floppy doesn't eject, which I guess means a drive motor or support electronics is shot. For perspective, Apple still wants like $150 for a new floppy, mail order sources have the same for about $70, and reliable refurbs run the gamut >from a low of about $20 up to $50 or more (used OK drives are $10 to $20. and my last pesky supplier was asking $5 for untested pulls). What I am finding disturbing is that more and more of the drives I see have OBVIOUSLY been swapped from another machine, or show other signs of being opened up by non techs (missing screws or other parts). What are your opinions, practices, or sources? Do any of you fix your floppies? Thanks.

27 years, 3 months

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stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5 1/4 floppies)

by edick＠idcomm.com

Well, perhaps you're right about the discussions you recall, Eric. I do recall that there was an effort afoot to use 80-track drives to read some diskettes written with the off-track method used by (Bill Budge?) games, etc, in order to defeat their copy protection. I do recall the comment being made, however, that a while person might defeat that particular copy protection, since the mechanism under discussion was capable of putting a track literally anywhere on the diskette, ( which certainly couldn't have been done with a stepper ) the protection scheme wouldn't hold up. In any case, it's good someone else was paying attention at the time, as it didn't really matter to me, though I found it interesting. It was, after all, over 20 years ago. Dick -----Original Message----- From: Eric Smith <eric(a)brouhaha.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, April 07, 1999 8:37 PM Subject: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5 1/4 floppies) >"Richard Erlacher" <edick(a)idcomm.com> wrote: >> (2) - I remember lengthy discussions among those members of the Denver Area >> 6502-Users' Group who were presumably qualified to discuss the intricacies >> of the internals of APPLE's disk I/O routines at a level I neither knew nor >> cared about, beyond the superficial details I gleaned from the several and >> varied sessions discussing that set of details. Now, I attended these >> weekely and typically 4-hour long meetings for several years, and KNOW the >> guys who were hashing out the details of the hardware and software in >> question knew what they were talking about, so I accept that as fact. > >Then, as you'll recall, I was one of the people who spoke at those meetings >regarding the operation of the Disk ][. Armed with information provided by >Wayne Wall, Larry Fish, and Peter Boyle, I delved into the disk system in order >to figure out how to defeat various copy protection schemes, including the >various half-track and quarter-track positioning methods. Larry was involved >in Apparat's efforts to interface standard Teac FD55 series disk drives to >the Apple ][ controller. > >> These fellows >> spent a couple of sessions talking about and demonstrating the screwy means >> by which certain game vendors in the Apple market were "protecting" their >> wares by altering the timing of the positioning routine, thereby making it >> possible to write tracks "off the track" by changing the time delay between >> a known cylinder position and the point at which the specific track was to >> be written. This made it impossible for someone using the stock timing of >> the positioning mechanism to read the diskettes so written. > >No, the postioning that was discussed was the half-track positioning I >described earlier. If you look at the Apple RWTS routines (for either 13- >or 16-sector diskettes), you'll find that the low level postioning routine >actually takes an argument that is two times the track number. > >The only thing about it that was non-obvious was the timing of the >acceleration/decelleration profile used to speed up the seek process. >However, this did not affect the final head position. > >> The scheme with the tristate multiplexers came later, I believe, than the >> one I remember. > >I'm not sure what tristate multiplexers you're referring to. The controller >for the Disk ][ never changed in any non-trivial way. Some later cards for >use with the Unidisk and Duodisk used a 19-pin D-subminiature connector in >place of the pair of 20-pin right angle headers, but the electronics was the >same. Starting with the Apple ][c they used the IWM chip, which was a >slightly fancier single-chip version of the original controller, but the >positioner control method didn't change. > >> Apple had several patents, all of which are there to be >> examined if one wishes. I believe this software-timed positioning scheme >> was among them. > >They had exactly one patent from that era which covers the disk controller. >It describes (among other things) how they use a stepper motor for positioning. > >> I doubt, however, that Wayne Wall would have allowed the waste of >> several sessions of the meetings he so firmly controlled back in those days, >> if the assumptions presented as fact in those discussions had not been >> verified. > >I'm sure he wouldn't have. Which is why there was not any discussion of >using DC motors for head positioning. > >> The helical cam I remember didn't have a groove, but rather, a ridge or > >Regarding mechanical details of the Disk ][ drive I'll readily concede that >you are likely correct, as I never bothered to study the mechanism, only >the electronics and code. > >Cheers, >Eric

27 years, 3 months

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Heatkit 5 1/4 floppies

by edick＠idcomm.com

Let me qualify this, first of all, with two bits of fact . . . (1) - I didn't care about the APPLE drives because they didn't work with the type of controller I produced, so if I'm wrong, it's caused little damage so far . . . and (2) - I remember lengthy discussions among those members of the Denver Area 6502-Users' Group who were presumably qualified to discuss the intricacies of the internals of APPLE's disk I/O routines at a level I neither knew nor cared about, beyond the superficial details I gleaned from the several and varied sessions discussing that set of details. Now, I attended these weekely and typically 4-hour long meetings for several years, and KNOW the guys who were hashing out the details of the hardware and software in question knew what they were talking about, so I accept that as fact. If it wasn't true, no harm done, but I doubt that was the case. These fellows spent a couple of sessions talking about and demonstrating the screwy means by which certain game vendors in the Apple market were "protecting" their wares by altering the timing of the positioning routine, thereby making it possible to write tracks "off the track" by changing the time delay between a known cylinder position and the point at which the specific track was to be written. This made it impossible for someone using the stock timing of the positioning mechanism to read the diskettes so written. The scheme with the tristate multiplexers came later, I believe, than the one I remember. Apple had several patents, all of which are there to be examined if one wishes. I believe this software-timed positioning scheme was among them. Having said that, I would point out that, given a software scheme sequenced the stepper, it is just as possible that one could have read the diskettes written a half track off by fiddling with the stepping sequence. I doubt, however, that Wayne Wall would have allowed the waste of several sessions of the meetings he so firmly controlled back in those days, if the assumptions presented as fact in those discussions had not been verified. The helical cam I remember didn't have a groove, but rather, a ridge or "fence" in the shape of a helix, which was tracked by a small, spring-loaded, roller bearing. This worked quite well, but, because of inertia and resonances in the system, required an unduly long period to settle. The somewhat more costly band-actuator positioned drives settled in 3ms, typically, a rate which could be advertised and made a drive look "better," although FDC's for the smaller drives had been designed such that the faster step rate couldn't be exploited without fancy external gyrations involving increasing the oscillator rate, since, previously, the mini-floppies, as they were then called, could seldom step faster than 6ms per track. By the time the IBM PC became available, all the drives you saw were capable of the fast step rate, yet IBM's hardware/software wouldn't readily accomodate it. There were freebie patches published by third parties to speed up the step rate, which caused the drives to quiet down considerably. Dick -----Original Message----- From: Eric Smith <eric(a)brouhaha.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, April 07, 1999 6:16 PM Subject: Re: Heatkit 5 1/4 floppies >"Richard Erlacher" <edick(a)idcomm.com> wrote: >> Apple drives >> used a form of GCR on their drives, the heads of which were positioned with >> a software timed DC motor, while nearly everyone else used FM or MFM on >> drives which used steppers driving band actuators. > >Correct about GCR, but not about head positioning. If you look at the >schematics of the Disk ][ controller card and that of the drive, both of >which were in the DOS reference manuals up through the early 3.3 manuals >(before the Apple //e shipped), you will see that the controller uses four >outputs of a 74LS259 (or 9334) 8-bit addressable latch to control the four >phases of the head positioning stepper motor. > >IIRC, in the drive the four TTL-level phase signals from the controller >are inputs to a ULN2003 which actually drives the motor phases. > >The stepper motor has an additional stable states halfway between any pair >of adjacent tracks. However, due to the head width, it was not possible to >get twice the number of usable data tracks. But you could use non-standard >track positions as long as they were at least two steps apart. One of the >earliest copy protection schemes was to use track 0, 1.5, 2.5, 3.5, etc. >Of course, the copy programs quickly started supporting half-track >positioning. > >The screwy part of Apple's head positioning system is the absence of a track 0 >sensor. The technique to home the positioner was to step away from track 0 a >few steps (call it N), then step toward track 0 by more than 68+N steps >(the number 96 comes to mind but I could be mistaken). This results in the >famous "Disk ][ mating call" sound. > >In fact, you can actually get quarter-track positioning, but you >have to keep one (two?) of the stepper coils driven to hold the positioner >in place. This can be viewed as a very crude form of microstepping. > >Of course, you can potentially also write data *during* the postitioner >motion. However, this was seldom done even for copy protection, because >the repeatability was poor even on the same drive, and very poor between >drives. > >Because the stepper motor was under software control, the RWTS subroutines >(Read/Write Track & Sector, the low-level disk driver) actually used a >ramped acceleration/deacceleration profile, for faster seek times than >in typical systems which used a fixed track-to-track step time. > >Eric

27 years, 3 months

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Apple GCR

by CLASSICCMP＠trailing-edge.com

>Can someone explain how the Apple II GCR worked? I tried deciphering this >several years ago and I could figure it out (the only references I found >were very vague). There's one reference which is extremely non-vague: _Beneath Apple DOS_, by Don Worth and Peter Lechner. In it you'll find wonderful illustrations featuring Sir Isaac Newton and leading you through the wonderfully intertwined world of the Disk ][ state machine, 6502 machine code, and modulation formats. This book is still available new (see my past posts to comp.sys.apple2 for details on how to buy it.) If you're too cheap to buy the book (again, buy the book! It's worth every last cent!), the relevant section of it (minus the cute drawings) is online at http://www.umich.edu/~archive/apple2/misc/hardware/disk.encoding.txt But, again, buy the book! Woz is not my super-hero, but he could do amazing things with a half-dozen TTL chips, that everyone else was doing with a hundred or more... -- Tim Shoppa Email: shoppa(a)trailing-edge.com Trailing Edge Technology WWW: http://www.trailing-edge.com/ 7328 Bradley Blvd Voice: 301-767-5917 Bethesda, MD, USA 20817 Fax: 301-767-5927

27 years, 3 months

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looking for a multibus memory card

by lemay＠cs.umn.edu

If anyone has a 4 meg multibus memory card that they would consider parting with, I could sure use one in my old sun workstation. -Lawrence LeMay

27 years, 3 months

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Hallelujah!

by drbilling＠ucdavis.edu

>On Mon, 5 Apr 1999, Derek Peschel wrote: > >> I was going to mention RPG in my original post but I changed my mind. ... > ... >Believe it or not people still use that abomination. ... > >Its funny because it's programmed much like the earlier versions of >ForTran, where each statement and associated arguments and data must start >in a particular column due to its origins as a punched card language. > >I would hope the latest version of RPG does away with the archaic column >specificity. Don't know about the latest versions of RPG, but it should not be forgotten that RPG was developed as an emulator for the 407 Tab machine. You could use it to turn a 1401 with a very small memory, i.e. 1.2K, into a 407 Tab machine, thusly you could turn the legion of 407 plug board programmers into computer programmers. One 1401 could do the same amount of work as several 407 Tab machines, much to the chagrin of IBM because the rent on one 1401 could be less than the rent of three 407s, depending on the configurations of each. -- Dean

27 years, 3 months

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Flopyy disk.

by drbilling＠ucdavis.edu

At 11:31 AM 4/7/99 -0700, Sellam wrote: >... >I tried to get him to speak at VCF 2.0 after he got axed by Conner (was it >Conner?) but I could never get ahold of him. I think he would have a good >story to tell so I may try again this year. Finis Conner worked for Al Shugart years ago, then left to start his own company. A couple of years ago it was in trouble and Shugart bought Conner Peripherals, but Finnis Conner soon departed. Last year sometime the board of directors of Seagate terminated Al Shugart's contract. -- Dean

27 years, 3 months

1
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Classic Adventures

by clintw＠colorado.cirrus.com

> > I was doing a bit of research and came across an interesting page: > > http://www.lysator.liu.se/adventure/ > > lists adventure games for various computers, including machines like the > PDP series and the much, much better (and far too infrequently mentioned) > HP 3000. 8^) > > Ahhh.... Adventure.... All the plugh's and plovers and xyzzy's you could shake a stick (of dynamite) at.... Does anyone remember a version that: If you went down from the hall of the Mt. king, you were in a room with a vault door. If you tried to apply any of the standard magic words (xyzzy etc) the door would fuse shut and something (a blob? a djinn?) would show up several turns later, chase you down, and kill you? It ran on a CPM machine in the early 80's. clint

27 years, 3 months

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Classic Adventures

by sinasohn＠ricochet.net

I was doing a bit of research and came across an interesting page: http://www.lysator.liu.se/adventure/ lists adventure games for various computers, including machines like the PDP series and the much, much better (and far too infrequently mentioned) HP 3000. 8^) --------------------------------------------------------------------- O- Uncle Roger "There is pleasure pure in being mad roger(a)sinasohn.com that none but madmen know." Roger Louis Sinasohn & Associates San Francisco, California http://www.sinasohn.com/

27 years, 3 months

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Heatkit 5 1/4 floppies

by edick＠idcomm.com

8" drives typically spun all the time, as their motors were AC types. If your 5-1/4" drive spins all the time, something's wrong. They had a nMOTOR_ON signal which you can monitor to determine whether it's a defective drive or a bunged-up driver. One important reason for the popularity of the smaller drives over the AC-powered 8" types was noise. If the drive is running all the time, clearly there's something wrong. It could be in the jumpering of the drive or in the controller firmware. It could even be a jumper option on the controller. You'll ruin lots of floppies in a drive which doesn't stop and which doesn't unload its heads. It's easy to monitor the control signals. If the controller tells the disk drive to keep spinning, you need to "fix" the BIOS code. Dick -----Original Message----- From: Joe <rigdonj(a)intellistar.net> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 9:13 AM Subject: Re: Heatkit 5 1/4 floppies >At 09:43 PM 4/7/99 -0700, you wrote: > >People today don't realize that the old >>systems used a floppy like present systems use a hard drive, almost all the >>time, which is a heck of a lot of wear for a contact media. > > I used to work for Burroughs and they had a computer that used 8" >floppys that spun continously. Burroughs said to replace the disks every >100 hours. I have no idea how long they would actually run before failing. > Does anyone know? I have a CPM machine that spins it's 5 1/4" disk >continously but I haven't run it enough for a disk to fail. > > Joe >> >> >

27 years, 3 months

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sending you a book?

by sring＠uslink.net

I received this message and I do not know what it is about! Stephanie sring(a)uslink.net -----Original Message----- From: Derek Peschel <dpeschel(a)u.washington.edu> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, April 07, 1999 4:16 AM Subject: Re: sending you a book? >I asked you about a book I got for you; you seemed interested but I still >want to confirm. Also I need your postal address. > >-- Derek >

27 years, 3 months

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Heatkit 5 1/4 floppies

by edick＠idcomm.com

Not all mini-floppy drives have the ability to load/unload the head. If yours doesn't, it's advisable to fix the spin-up/spin-down problem with either software or hardware, i.e. jumpers or the like. The decision to go ahead and wear down the emulsion of your floppy diskette was made when drives and media were common. That's no longer the case, and since you're into retrocomputing, the slower(oops, I mean "more realistic") it is, the better you'll like it, right??? The last time I checked (a long time ago) my CP/M-ulator ran at 6-7x the speed of the "real McCoy" so I doubt you're running the old hardware just to run those old programs. While it's true that 8" drives can run constantly without media or head damage they had head-load solenoids as opposed to a spring which loads the heads once the drive door is closed as the mini-floppies often do. The emulsion on a floppy diskette becomes increasingly abrasive as the emulsion ages and, not only will it dirty the heads by leaving whatever dust or other glutch is present on the diskette in the head gap, but it will polish and grind on your heads. If you want your heads worn and dirty, running them in constant contact with the media and spinning will do it just fine. Dick -----Original Message----- From: Joe <rigdonj(a)intellistar.net> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 1:21 PM Subject: Re: Heatkit 5 1/4 floppies >Dick, > > I don't know if they're supposed to run all the time or not, but both >drives do it so I don't think it's a problem in the drives. A lot of the >older drives had jumpers to cause them to run continously. I guess it >saved the time needed to spin the drive up to speed. Several people have >said that they have systems with 5 1/4" drives that spin all the time so it >may be normal. Allison says that her 8" drives have run thousands of hours >without problems so I hope it's not a problem. > > Joe > >At 11:50 AM 4/8/99 -0600, you wrote: >>8" drives typically spun all the time, as their motors were AC types. If >>your 5-1/4" drive spins all the time, something's wrong. They had a >>nMOTOR_ON signal which you can monitor to determine whether it's a defective >>drive or a bunged-up driver. One important reason for the popularity of the >>smaller drives over the AC-powered 8" types was noise. If the drive is >>running all the time, clearly there's something wrong. It could be in the >>jumpering of the drive or in the controller firmware. It could even be a >>jumper option on the controller. You'll ruin lots of floppies in a drive >>which doesn't stop and which doesn't unload its heads. It's easy to monitor >>the control signals. If the controller tells the disk drive to keep >>spinning, you need to "fix" the BIOS code. >> >>Dick >>-----Original Message----- >>From: Joe <rigdonj(a)intellistar.net> >>To: Discussion re-collecting of classic computers >><classiccmp(a)u.washington.edu> >>Date: Thursday, April 08, 1999 9:13 AM >>Subject: Re: Heatkit 5 1/4 floppies >> >> >>>At 09:43 PM 4/7/99 -0700, you wrote: >>> >>>People today don't realize that the old >>>>systems used a floppy like present systems use a hard drive, almost all >>the >>>>time, which is a heck of a lot of wear for a contact media. >>> >>> I used to work for Burroughs and they had a computer that used 8" >>>floppys that spun continously. Burroughs said to replace the disks every >>>100 hours. I have no idea how long they would actually run before failing. >>> Does anyone know? I have a CPM machine that spins it's 5 1/4" disk >>>continously but I haven't run it enough for a disk to fail. >>> >>> Joe >>>> >>>> >>> >> >> >

27 years, 3 months

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Fooling with floppy drives

by SUPRDAVE＠aol.com

In a message dated 08/04/99 10:22:43 Eastern Daylight Time, edick(a)idcomm.com writes: << Since new floppy drives cost about $25 including shipment, it's difficult to justify repairing them. This is frustrating for people like you who have drives for which replacements are not readily available for $20 or so. Your experience with sloppy workmanship gives clear indication that $10 per hour is not enough to pay a competent technician. The occasional look inside should give you good indication of why one who can't spend more than 15 minutes' time fixing a $20 drive, can't get the job done. These devices must be considered "throw-away" items by now. You've got to learn to fix-em-yourself. >> agreed, but i'd only apply this throw away mindset to ordinary pc floppy drives. mac suprdrives are hard to find and expensive. i've one now in my mac IIx that's not reading any disks. apple drives are plentiful and cheap, but i'd fix them as well since none are produced anymore, obviously.

27 years, 3 months

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Fooling with floppy drives

by edick＠idcomm.com

Since new floppy drives cost about $25 including shipment, it's difficult to justify repairing them. This is frustrating for people like you who have drives for which replacements are not readily available for $20 or so. Your experience with sloppy workmanship gives clear indication that $10 per hour is not enough to pay a competent technician. The occasional look inside should give you good indication of why one who can't spend more than 15 minutes' time fixing a $20 drive, can't get the job done. These devices must be considered "throw-away" items by now. You've got to learn to fix-em-yourself. Dick -----Original Message----- From: Mike Ford <mikeford(a)netwiz.net> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 08, 1999 2:29 AM Subject: Fooling with floppy drives >Coincident with all this chatter on floppy drives I have run into a streak >of uncooperative drives. I happen to be using macs with 3.5" Sony >mechanisms, but my question is somewhat general. What do you do with floppy >drives that need repairs? > >Normally I just put them aside, but after this week I have close to a dozen >in the defective box and ZERO (actually a negative number since I need even >more) reliable units that aren't already installed in other systems. > >I have already performed the first aid procedures like cleaning the heads >(using a wet cleaning floppy), and disassembly down to the bare mechanism >and blowing out the bunnies with canned air. This pile is the hard core >rejects, floppy doesn't spin, floppy doesn't eject, which I guess means a >drive motor or support electronics is shot. > >For perspective, Apple still wants like $150 for a new floppy, mail order >sources have the same for about $70, and reliable refurbs run the gamut >from a low of about $20 up to $50 or more (used OK drives are $10 to $20. >and my last pesky supplier was asking $5 for untested pulls). What I am >finding disturbing is that more and more of the drives I see have OBVIOUSLY >been swapped from another machine, or show other signs of being opened up >by non techs (missing screws or other parts). > >What are your opinions, practices, or sources? > >Do any of you fix your floppies? > >Thanks. > >

27 years, 3 months

3
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potholes

by steverob＠hotoffice.com

On Thursday, April 08, 1999 6:16 AM, Charles E. Fox [SMTP:foxvideo@wincom.net] wrote: > > Did anyone catch the bit on ABC news last night about the use of old > computers to fill potholes? > I think some of our Windsor potholes would require at least a mini. > > Regards Here's the story: http://www.cnn.com/NATURE/9904/07/computers.potholes.ap/ Steve Robertson <steverob(a)hotoffice.com>

27 years, 3 months

1
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Lisp, the machine language. Was Re: Hallelujah!

by hhacker＠home.com

It is interesting to me that others view Lisp as a high level language. For my money, it is an assembly language for an abstract computer. Sure, it has much of the form of a high level language but, the simplicity of its minimal number of required operators makes it ideal as a machine language. As I recall, CAR, CDR, CONS, and four or five more operators is all that is necessary for a complete implementation. This is RISC processing if ever there is such a thing. Moreover, the fact that all things are handled as a single data type sure does imply an object point of view, however much that point of view is myopically constrained (that the objects are all lists!). The most interesting aspect of Lisp, for me, is that code can be constructed by the operation of a program, and thereupon caused to be executed. This is another parallel with machine languages. William R. Buckley

27 years, 3 months

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Heatkit 5 1/4 floppies

by edick＠idcomm.com

I don't believe those were the earliest of the 5-1/4" types. The early SA-400's I remember used a lead screw just like the 8" drives, but that was too costly for the competition that followed. When Apple started buying "partial" drive mechanisms in order to implement their more software-driven approach, with the idea of saving a few bucks . . . multiplied by a milion or two drives . . . other manufacturers including SIEMENS and BASF, among others, tried a two-phase stepper on a helically-tracked drive wheel as opposed to the stepper driving a lead screw. Most makers later went to a band-actuator system using a small stepper. Since the business of designing floppy and hard disk controllers was my long suit back then, I had several of nearly every type of FDD and HDD lying around the shop, and there were LOTS. By the time IBM got into the game, the positioning mechanism contest was pretty well settled. Apple drives used a form of GCR on their drives, the heads of which were positioned with a software timed DC motor, while nearly everyone else used FM or MFM on drives which used steppers driving band actuators. Once the volume was up, the cost wasn't that much greater, while the precision and accuracy were quite a bit greater. I don't even remember what the nature of the physical linkage between the motor an the head positoner was, since I stayed away >from them. I still have an Apple drive somewhere. I suppose I could look . . . Of course, Apple's orientation toward YOUR data was that nobody really cared if you had to punt and hit the reset button just because the FDD wouldn't read the floppy it wrote just a few minutes before . . . After all, if you were serious, you didn't use an Apple. If you were serious it's for sure you had some 8" drives for the data you wanted to keep. Dick -----Original Message----- From: James Willing <jimw(a)agora.rdrop.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, April 07, 1999 1:57 PM Subject: Re: Heatkit 5 1/4 floppies >On Wed, 7 Apr 1999, Jeffrey l Kaneko wrote: > >> These were in common use on Z89's and Z-90's. Heathkit used drives made >> by >> Tandon and Siemens. The Siemens drives were kinda unique: It used a >> disk with a spiral groove for the head positioner. > >Hmmm... hardly that unique it would seem... The Shugart SA-400 series >drives used that same positioning systems (first?). > >-jim >--- >jimw(a)agora.rdrop.com >The Computer Garage - http://www.rdrop.com/~jimw >Computer Garage Fax - (503) 646-0174 >

27 years, 3 months

9
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Microsoft is about to arrest me!

by lemay＠cs.umn.edu

Well, I just bought something at a used bookstore called "SOFTCARD; VOLUME II" Its a microsoft product, and apparently its illegal to even give it away, let alone to resell it ;) I'm going to ignore that obviously illegal wording ;) Apparenly this is the software and manual for the Microsoft Z80 card for the Apple II series. I have one floppy disk, never used, in 16-sector format for DOS 3.3 or language card. Apparently there should be another manual with chapters 1-3 (unfotunately these are the more interesting chapters), whereas this is chapter 4 on the latest and greatest microsoft basic ever created, which is apparently on the floppy disks ;) plus a little information in the final chapter 5. I dont suppose i can use any of this without the Z80 card? The cp/m wont work without it i'm guessing. Am I correct in guessing all this is good for is Ebay or trades? -Lawrence LeMay PS: I also picked up a nice copy of "the programmers CP/M handbook" which provides extensive coverage of CP/M 2.2, mainly assebly listings. It looks like more than 50% of it is assembly listings. Interesting... PPS: I really should go back and buy that UCSD P-system book, I suppose.

27 years, 3 months

6
5
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microcode, compilers, and supercomputer architecture

by yakowenk＠cs.unc.edu

On Tue, 6 Apr 1999, ard(a)p850ug1.demon.co.uk (Tony Duell) wrote: ] > To put this slightly on topic, we all know that computer systems have ] > become more reliable in the last 20 years but does anyone have any real ] ] I am not totally convinced. Computers have become a lot more complicated ] in the last 20 years, and IMHO some of that complexity has led to ] unreliablity (cf the comparative crash rate of say Windows and CP/M). I am totally unconvinced. :-) The number of times per day that I run into something that doesn't work has steadily gone up over the years. Years ago, although the machine might crash from time to time, it would generally work pretty well. Nowadays, even when the machine is "working", I have to wait for the characters that I type to show up on my screen, and programs that I run every day will often refuse to work because some server that I've never even heard of is down or unreachable. Prediction: between ten and twenty years from now, somebody will discover "standalone" computing; that a computer can be made to function even when not attached to a network. It will be a revolution, paving the way for systems that keep working once they are set up, even with evil sysadmins reconfiguring everything they can get their hands on three times a week. ] Also, I have had _far_ more built-to-a-price PC parts land on my bench to ] be repaired than (say) DEC PDP11 and PDP8 parts. For all I have had to ] maintain many _more_ of the latter type of machine. ] ] -tony

27 years, 3 months

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