test-drb April 1999

test-drb@ccmp.vtda.org

170 participants
1190 discussions

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

by edick＠idcomm.com

Well, if you look at the 6502 architecture very carefully, you'll see what a thing of beauty it really is. What the 8080 and Z-80 designers did with brute force, the 650x designers did with resourceful elegance. Instead of big counters and the like, for, say, the stack pointer or the program counter, the 650x needs only to use registers. The same ALU that is used in the execution of instructions is useable to increment the program counter, manipulate the stack pointer, etc. The part can be built with extremely little in the way of resources. I once sat down with a pencil and figured out that you could build the content of the 6502 with a pair of 74181's, a pair of 74189's four '373's a couple of decoders, a small PAL and a 256x12 rom (3 82S129's) That was all available in '75 or so, with the possible exception of the PALand the 373's. That is not very much logic. That was possibly what they used to prototype their part. Think about it! It's really simple and you could easily build it as part of a gate array. Try that with a Z-80 and see what you get. Dick -----Original Message----- From: Allison J Parent <allisonp(a)world.std.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Sunday, April 11, 1999 6:08 PM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 51/4 floppies) ><I'm not sure I'd agree, when it comes to indexing. I think the 6502 ><indexing is more useful in typical cases, and the instruction set is much ><"cleaner" in some ways. However... > >it has to be as there are so few register to store intermediate results or >addresses. The end result is operands are out in memory more and return to >memory more. Different optimization of resources. > ><Exactly. I was brought up on the Z80, or at least that's what my earliest ><assembly language experience was on, but I learned how to use a 6502 prett ><well. Just a different design philosophy. > >the oder of learning for me was PDP-8, PDP-10, CM2100, 8008, 8080 then >over a span of 6 years. From the 1975 to 1978 the list is z80, 8048, > 1802, sc/mp, 6800, 650x, 9900, pdp-11! > >I have fewer biases. ;) Well ok, if said 8085 for some, 804x for others, >T-11 (pdp-11 on a single chip), and z80. Never had more than the few 6502s >until recently but they are fun too. > >Allison >

25 years, 9 months

PR1ME 2550 Up and Running

by jpl15＠netcom.com

Well... it didn't hurt as much as I thought it was going to.. I have just run "SHUTDN ALL" after two hours of playing with PRIMOS (on a DEC LA120 running at 300 baud... s-l-o-w...). I rescued this system about two months ago, and finally got tired of it taking up space. It took about an hour to figure out where all the cables used to go, and the Control Data SMD drive [used as a paging and swapping drive] needed a little prodding to wake it up, but the system boots and remembers what it was doing last time it was on... about six years ago. Now to try and make the console port run at a decent speed. And, apropos of the Pick discussions, this machine has INFORMATION loaded and running... haven't messed with it yet, tho.. Cheers John

25 years, 9 months

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

by edick＠idcomm.com

You can build your own in an FPGA for something on the order of 2500 gates. That will ostensibly operate at 80 MHz or so. Some vendors make claims about their silicon that sport higher speed claims, e.g. 150-200 MHz. I'll believe the 80 is realistic. Dick -----Original Message----- From: Allison J Parent <allisonp(a)world.std.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Sunday, April 11, 1999 4:36 PM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 51/4 floppies) ><Well, that's not very far from what I wrote, is it? I was just pointing ><out that although Allison seemed to imply that a 6 or 8MHz Z80 was much ><faster than a 4MHz(? I haven't got the original message any more) 6502, I ><believe that to be far from the case. > >I was pointing out that is the processor was running fast enough even a >dog can look good. ;) Obviously using a 8mhz z80 as the standard your >comparison CPU had better be of similar generational speed or it may fail >the test. the inverse is with a 33mhz z185 I know I can blow the 65c02 >out of the water unless someone has at least a 25-30mhz 6502! > >Allison >

25 years, 9 months

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

by allisonp＠world.std.com

<I'm not sure I'd agree, when it comes to indexing. I think the 6502 <indexing is more useful in typical cases, and the instruction set is much <"cleaner" in some ways. However... it has to be as there are so few register to store intermediate results or addresses. The end result is operands are out in memory more and return to memory more. Different optimization of resources. <Exactly. I was brought up on the Z80, or at least that's what my earliest <assembly language experience was on, but I learned how to use a 6502 prett <well. Just a different design philosophy. the oder of learning for me was PDP-8, PDP-10, CM2100, 8008, 8080 then over a span of 6 years. From the 1975 to 1978 the list is z80, 8048, 1802, sc/mp, 6800, 650x, 9900, pdp-11! I have fewer biases. ;) Well ok, if said 8085 for some, 804x for others, T-11 (pdp-11 on a single chip), and z80. Never had more than the few 6502s until recently but they are fun too. Allison

25 years, 9 months

Restoring an 8/E

by mbg＠world.std.com

>The data lights were ok the address lights I remember a high order >one bad. Actually, I was back over at my museum earlier this evening, to put the cleaned and repaired front panel on the 8/e... I took the time to power it up myself, and did a little playing with loadadrs and dep... I verified that I can address both fields (0 and 1)... it has 8k. I checked the EMA lights, and they all light. I tested the address lights and they all light... I checked out the data lights, they all light, at least in MD position... I've yet to check the other positions... Megan Gentry Former RT-11 Developer +--------------------------------+-------------------------------------+ | Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com | | Unix Support Engineering Group | (home): mbg!world.std.com | | Compaq Computer Corporation | addresses need '@' in place of '!' | | 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ | | Nashua, NH 03062 | "pdp-11 programmer - some assembler | | (603) 884 1055 | required." - mbg | +--------------------------------+-------------------------------------+

25 years, 9 months

8/E cable handling?

by cmcmanis＠mcmanis.com

Ok, I was wondering how the 8/E manages its cables. In the 8/f/m chassis there is a sliding door with a plate on it to act as a strain relief and exit point for cables exiting the CPU chassis. I don't think I want to put something in the cover I'm building but I really think the strain relief is necessary (I've seen M8650 boards with one connector broken off because of a pull on the cable and there wasn't anything to take the strain) Anyway, thoughts appreciated, --Chuck

25 years, 9 months

Restoring an 8/E

by allisonp＠world.std.com

<You mean you _don't_ have a pile of PDP11 power control cables to raid <suitable plugs from ? She does, they were in another box...under a box... <Nice!. It's worth testing all the panel lamps (just load an address of <all 1's, store data of all 1's to location 0, etc). A blown bulb can make <debugging a program rather hard... The data lights were ok the address lights I remember a high order one bad. Allison

25 years, 9 months

Don Lancaster was Re: Ebay Mark-8 Plans

by jlewczyk＠his.com

Actually, He was on the scene very early, accoridng to me sources. I have copies of the very first Mark-8 computer newsletters and he was a contributor, providing some detailed information on building quality power supplies. His name was on the list of newsletter receipients from the beginning. And this was 1974, so yeah, he meets the >10 rule! :-) > I know that he cammme on the scene later than some of > the other people who have been mentioned as past or future > VCF speakers, but he certainly meets the >10 rule.

25 years, 9 months

What if,... early PCs (was: stepping machanism

by allisonp＠world.std.com

<While I agree, I kinda doubt that Allison has EVER plugged in ANYTHING <before she "opened the box and added a bunch of stuff/mods". So, she <might not see that as quite the negative that you do :-) Not quite true. I'd make sure it works then mod it if needed. :) the first mod I ever did to a trs80 was the add a ram and wire to get lower case. <open. But it is true that RS had a very bad attitude about it. They <actually had anti-tamper paint on one of the screws! One of the local RS <technicians had an interesting slant on that: Since RS's policies <apparently didn't explicitly mention modifications, only that the tamper <seal must be intact, he would happily do the various warranty mods (there <were SEVERAL for the early EI), IFF you provided him circuit sketches for <all mods, and put a dab of the anti-tamper paint (he would provide it) on <the screw after you made the mods. He said that if the store manager <balked at seeing additional stuff through the slots of the "unopened" <case, just start talking about "building boats in bottles". Apple's <attitude of "go on in!" was much more refreshing. Most of the techs (me too, back then) held that the worst part of fixing TRS80s was first correcting the messes customers made. Often with soldering tools better suited for fixing pipe. We didn't care the mods existed and later Tandy would even sell a few as options. <> IBM really performed only one major service to the microcomputer world: <> They lent it its own trade name, which was its legitimacy. <"PC" was in moderately common usage around here before IBM's entry. <IBM always considered "PC" to be a shortened description, NOT a trade <name! They did NOT trademark "PC". They never even trademarked <"PC-DOS"!! OTOH, "MS-DOS" IS a registered trademark. The upside is a lot of other systems got in where before computers were not taken seriously beacuse if they were IBM would be doing it. <One fellow referred to Compaq's "challenge" of IBM as "a mouse running up <the elephant's leg with intent to rape". Looking back... I bet the elephane didn't even scream. ;) Allison

25 years, 9 months

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

by pete＠dunnington.u-net.com

On Apr 11, 18:27, Allison J Parent wrote: > I was pointing out that is the processor was running fast enough even a > dog can look good. ;) cf any recent pentium :-) -- Pete Peter Turnbull Dept. of Computer Science University of York

25 years, 9 months

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test-drb April 1999