test-drb

test-drb@ccmp.vtda.org

101090 discussions

by cmcmanis＠mcmanis.com

I rewired the plug on J3 to supply 5V at pin #3 (rather than going to the voltage regulator board) and both backplanes are now functional! Running Allison's worm program with the memory in back and the CPU and stuff in front. --Chuck

26 years, 8 months

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

by CLASSICCMP＠trailing-edge.com

>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

26 years, 8 months

[RANTISH] Programming Stupidity

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

> From: Sellam Ismail <dastar(a)ncal.verio.com> > To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> > Subject: Re: [RANTISH] Programming Stupidity > Date: Saturday, April 10, 1999 3:53 > > On Fri, 9 Apr 1999, Geoff Roberts wrote: > > > You've already lost if you have to run Windoze whatever. I'd switch to > > something more stable in a minute, but the sad part is that Windoze is > > everywhere, so we have to teach our students to use it and the apps that > > run on it, because that's what they will likely find in the real world.. > > So are you preparing your students for 1 or 2 years out, or are you > preparing them for a lifetime? If you're just preparing them for the > first few years of their career, keep teaching them windows. Tell it to the employers. They ask for people with computer skills. But what they really want is people that are skilled in the use of Word, Excel and Access. When that situation changes, we'll happily shift to Linux or similar. For now, it has to be left to the University (we're Reception to Year 12, ie; Primary/High School) to teach about real operating systems etc. > However, if you want to give them the advantage over others that will > allow them to be more competitive, make more money and therefore get more > girls (and boys) start teaching them on Linux boxes. I'd like to do both, as Micro$oft skills are still very marketable, especially for young people in a high youth unemployment market. (Like around here) Sadly, very few companies/businesses within 100miles or so use anything but MS Office. (Apart from 2 ISP's) Cheers Geoff Roberts Computer Systems Manager Saint Marks College Port Pirie, South Australia geoffrob(a)stmarks.pp.catholic.edu.au

26 years, 8 months

Fooling with floppy drives

by SUPRDAVE＠aol.com

In a message dated 09/04/99 4:56:32 Eastern Daylight Time, mikeford(a)netwiz.net writes: << My plan right now is to first buy some more drives, then sit down with a batch and rubber gloves and clean and relube all of them at once. In fact I may seek out a box of "bad" floppies to add to my repair run next time I see them at the swap meet. Fortunately I just opened up a IIfx from a friendly trade and found two excellent condition drives (along with some giant double sized 8 MB simms). >> that's a good idea. better to find and hoard those old disk drives for parts than have them thrown away for good. that IIfx is nice machine also. treat those 8meg simms like gold. they're proprietary to the fx model.

26 years, 8 months

PDP-8/E PSU Debugging (was Q-bus pinout)

by allisonp＠world.std.com

PDP-8 tautology is clear, one only needs a set of DEC small computer handbooks to sort it out. My 1973 copy describes all three versions and their major differences very clearly. <Well, that's not how I read it. By my reading, Doug's writeup makes <it perfectly clear that 8/E's and 8/F's were produced simultaneously <and from a common pool of (largely, but not completely) compatible parts. Yes, and what isn't made clear is that pool of parts was an evolving one ove the years. <>The evolution vectors were as follows: <> Module updates - example M833 - M8330, M831 - > M8310 < <In the FAQ, Doug says on this subject: < <* Most of the early boards with 3 digit numbers were defective <* in one way or another, and the corrected boards added a trailing <* zero. Thus, the M833 was generally replaced with an M8330, and <* the M865 was replaced with the M8650. It was the easiest way to ducument the corrections at the modele level. the 54-class number changed as well. In later years depending on the change the module(s) (generic statment) would get letters tacked to the end (and the numbering would go from 2/5 to 2/5/2 and later to 2/5/2/3). <> Chassis updates - Long box, single OMNI BUS <> Long box dual OMNI BUS < <And in the FAQ Doug agrees with you: Long box single is an "as ordered" configuration variation if you ordered a plain 8E you would see one backplane. If you ordered a 32kw disk and tape system you can bet it would have two backplanes. A la carte connfiguration ordering was a PDP-8 characteristic and may have been a new concept to the industry. It was a very configurable machine. <There's no doubt that there were many ways to mix and match the <various components produced. I'm a bit uncertain why some folks <try to apply zoology so incessantly to their computers, when in real <life folks move parts between systems with wild abandon, but then <again zoology has always bored me to tears. That is also true to a point. But the E was always the long box and the F/M were shorter box and single bus. The fact that customers over 30 years would shuffle things around muddies the matters. then again the ability to do that is also an omnibus unique PDP-8 characteristic. Allison

26 years, 8 months

PDP-8/E PSU Debugging (was Q-bus pinout)

by CLASSICCMP＠trailing-edge.COM

>>That being said (and yes I've sent Doug mail on this but its not exactly >>FAQ material unless you really want to restore them as I do) I'd appreciate >>pictures for the cover on the long one since I can fabricate a cover then. >On mine, it's just a big sheet metal panel, with tabes on the right >that go into slots on the chassis and with tape-seal type latches on >the left. No ventilation slots at all. There's a lip on every edge >except for the rear. After reading Tony's reply, I now realize what your question must be about: the ventilation holes on the right-hand side. On mine, there are two, both 6.5 inches high, the front one 4.5 inches wide and positioned roughly over the third through thirteenth cards, the rear one 6 inches wide and positioned roughly over the 8th through the last slot of the second backplane unit. Both holes have a grill of hexagonal mesh, about 1/4" spacing, welded on the right hand side. Does this help? And, to be more explicit about the lips, the front and left lips are about 3/4" of an inch. And the back panel has two slots, each roughly 2 3/8" wide. I think my maintenance books might have a drawing; if I find one, would a fax of that page help? -- 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

26 years, 8 months

PDP-8/E PSU Debugging (was Q-bus pinout)

by CLASSICCMP＠trailing-edge.COM

>>I know that folks here have traiditionally objected to outside FAQ's >>when instead the issue could be resolved by dozens of E-mails, but in >>this case Doug Jone's *PDP-8 Summary of Models and Options* answers >>the question of 8/E vs 8/F quite nicely: >Too bad it's wrong. >It makes it seem as if there was a box that was designated PDP-8/E and it >had a particular configuration that was retired until the introduction of a >new box with the designation of PDP-8/F. This isn't supported by the evidence. Well, that's not how I read it. By my reading, Doug's writeup makes it perfectly clear that 8/E's and 8/F's were produced simultaneously and from a common pool of (largely, but not completely) compatible parts. >What really happened, and I have several independent confirmations of same, >is that the PDP-8/E system evolved into the PDP-8/F in a series of steps. >Depending on the date code the machine was configured differently. And I think that Doug Jone's FAQ entry agrees with you here. >The evolution vectors were as follows: > Module updates - example M833 - M8330, M831 - > M8310 In the FAQ, Doug says on this subject: * Most of the early boards with 3 digit numbers were defective * in one way or another, and the corrected boards added a trailing * zero. Thus, the M833 was generally replaced with an M8330, and * the M865 was replaced with the M8650. If you look in the PDP8-Lovers/alt.sys.pdp8 archives, you'll find Charles Lasner going into great detail about the differences between the different revisions of boards. > Chassis updates - Long box, single OMNI BUS > Long box dual OMNI BUS And in the FAQ Doug agrees with you: * There were many other internal options. There was room in the * basic box for another 20 slot backplane; taking into account the * 2 slots occupied by the M935 bridge between the two backplanes, * this allowed 38 slots > Short box single OMNIBUS Linear PSU on side. > Short box single OMNIBUS Switching PSU in rear. And again, in the FAQ Doug agrees with you: * The original PDP-8/F box had a defective power * supply, but a revised (slightly larger) box corrected this * problem. > Front Panel Updates: Diode logic + 8v LAMPS > TTL logic + 6v LAMPS > TTL logic + LEDs in lamp sockets > TTL Logic + LEDS And again Doug states that there were several front panel configurations. > PSU updates - Long linear PSU > Short linear PSU > Short Switching PSU (types A and B) And again Doug notes the difference in power supplies. >At some point in this evolution some marketroid decided to change the name >from 8/e to 8/f. The OEM version of this platform was called the 8/m and >included an optional limited function front panel (although all 8/M's I've >seen so far had the programmers panel but that's only about a dozen so who >can say) > >I happen to have an 8/e that is: > Short box > 6v LAMPs plus TTL front panel > Side mount PSU There's no doubt that there were many ways to mix and match the various components produced. I'm a bit uncertain why some folks try to apply zoology so incessantly to their computers, when in real life folks move parts between systems with wild abandon, but then again zoology has always bored me to tears. >My guess is that the evolution of the 8/E was driven by the introduction of >the 11/20 since these changes seem have occurred between 1970 and 1972. All >8/E's with date codes prior to 1970 appear to be the diode front panel >type, All 8/E's after 1972 appear to be either 8/F's or 8/Ms (until the 8/a >came out). Again, I think you're trying too hard to classify machines which were built from a hodgepodge of parts to fit each individual situation. Lots of 8/E's and 8/F's went into instruments, and generally the OEM could pick and choose the features they wanted. >That being said (and yes I've sent Doug mail on this but its not exactly >FAQ material unless you really want to restore them as I do) I'd appreciate >pictures for the cover on the long one since I can fabricate a cover then. On mine, it's just a big sheet metal panel, with tabes on the right that go into slots on the chassis and with tape-seal type latches on the left. No ventilation slots at all. There's a lip on every edge except for the rear. -- 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

26 years, 8 months

PDP-8/E PSU Debugging (was Q-bus pinout)

by CLASSICCMP＠trailing-edge.COM

>Chuck McManis <cmcmanis(a)mcmanis.com> wrote: >>Megan, was that a "long" 8/e or a "short" 8/e you recovered in your haul? >>If it was a long one could you take a couple of pictures of the cover for >>me? >What do you mean by a "long" 8/e... I thought the long box was the >8/e and the short one (what Allison has) an 8/f. I know that folks here have traiditionally objected to outside FAQ's when instead the issue could be resolved by dozens of E-mails, but in this case Doug Jone's *PDP-8 Summary of Models and Options* answers the question of 8/E vs 8/F quite nicely: Subject: What is a PDP-8/E? Date of introduction: 1970 (during or before August). Date of withdrawal: 1978. Also known as: PDP-8/OEM Industrial-8 (with a red color scheme) LAB-8/E (with a green color scheme) Price: $6,500 Technology: SSI and MSI TTL logic were used on these boards, and the entire CPU fit on 3 boards. Nominally, these were DEC M-series flip Chip modules, but in a new large format, quad-high (10.5 inch), extended-length (9 inch, including card-edge connector, excluding handles). The terms used for board height and length are based on the original working assumption that all flip-chips were plugged horizontally into a vertially mounted card-edge connector. On the PDP-8/E, the cards were plugged vertically down into a horizontally mounted connector, so many users incorrectly refer to these boards as quad-wide double-high. Interconnection between boards was through a new bus, the OMNIBUS. This eliminated the need for a wire-wrapped backplane, since all slots in the bus were wired identically. A new line of peripheral interfaces was produced, most being single cards that could be plugged directly into the inside the main enclosure. These included a set of posibus adapters allowing use of older peripherals on the new machine. Interboard connectors were needed for some multiboard options, including the CPU and memory subsystems. These used standard 36-pin backplane connectors on the opposite side of the board from the backplane. Some boards, notably memory boards, had a total of 8 connector fingers, 4 for the omnibus and 4 for interboard connectors. The core memory cycle time was 1.2 or 1.4 microseconds, depending on whether a read-modify-write cycle was involved (a jumper would slow all cycles to 1.4 microseconds). A 4K core plane was packaged on a single quad-wide double-high board, with most of the drive electronics packed onto two adjacent boards. Soon after the machine was introduced, an 8K core plane was released in the same format. Reason for introduction: The cost of the PDP-8/I and PDP-8/L was dominated by the cost of the interconnect wiring, and this cost was high as a result of the use of small circuit boards. By packing a larger number of chips per board, similar function could be attained in a smaller volume because less interboard communication was required. The PDP-8/E exploited this to achieve a new low in cost while attaining a new high in performance. Reason for withdrawal: This machine was slowly displaced by the PDP-8/A as the market for large PDP-8 configurations declined in the face of pressure from 16 bit mini and microcomputers. Compatability: As with the PDP-8/I and PDP-8/L, there are no limits on the combination of IAC and rotate instructions. Unlike the early machines, basic Group 3 OPR operations for loading and storing the MQ register work even if there is no extended arithmetic element. Finally, a new instruction was added, BSW; this swaps the left and right bytes in AC, and is encoded as a Group 1 OPR instruction using the "double the shift count bit". An odd quirk of this machine is that the RAL RAR combination ands the AC with the op-code, and the RTR RTL combination does an effective address computation loading the high 5 bits of AC with the current page and the lower bits of AC with the address field of the instruction itself! The EAE has a new mode, mode B. Previous EAE designs were single-mode. Mode B supports a large set of 24 bit operations and a somewhat more rational set of shift operations than the standard EAE. All prior EAE designs would hang on the microcoded CLA NMI (clear/normalize) instruction applied to a nonzero AC. This instruction is redefined to be a mode changing instruction on the 8/E. Standard configuration: A CPU with 4K of memory, plus 110 baud current loop teletype interface. Both a rack-mount table-top versions were sold (both 9" high by 19" wide by 21" deep). The rack mount version was mounted on slides for easy maintenance. The OMNIBUS backplane was on the bottom, with boards inserted from the top. The PDP-8/OEM had a turn-key front panel, no core, 256 words of ROM and 256 words of RAM, and was priced at $2800 in lots of 100. The standard OMNIBUS backplane had 20 slots, with no fixed assignments, but the following conventional uses; certain board sets were jumpered together (shown with brackets) and therefore were required to be adjacent to each other: -- KC8E programmer's console (lights and switches) -- M8300 \_ KK8E CPU registers -- M8310 / KK8E CPU control -- -- -- M833 - Timing board (system clock) -- M865 - KL8E console terminal interface. -- -- -- -- space for more peripherals -- -- -- M849 - shield to isolate memory from CPU -- G104 \ -- H220 > MM8E 4K memory -- G227 / -- -- -- space for more memory -- -- M8320 - KK8E Bus terminator Most of the early boards with 3 digit numbers were defective in one way or another, and the corrected boards added a trailing zero. Thus, the M833 was generally replaced with an M8330, and the M865 was replaced with the M8650. Expandability: The following are among the OMNIBUS boards that could be added internally: -- M8650 - KL8E RS232 or current loop serial interface. -- M8340 \_ Extended arithmetic element. -- M8341 / (must be attached in two slots between CPU and M833. -- M8350 - KA8E posibus interface (excluding DMA transfers). -- M8360 - KD8E data break interface (one per DMA device). -- M837 - KM8E memory extension control (needed for over 4K). -- M840 - PC8E high speed paper tape reader-punch interface. -- M842 - XY8E X/Y plotter control. -- M843 - CR8E card reader interface. There were many other internal options. There was room in the basic box for another 20 slot backplane; taking into account the 2 slots occupied by the M935 bridge between the two backplanes, this allowed 38 slots, and a second box could be added to accomodate another 38 slot backplane, bridged to the first box by a pair of BC08H OMNIBUS extension cables. Given a M837 memory extension control, additional memory could be added in increments of 4K by adding G104, H220, G227 triplets. The suggested arrangement of boards on the OMNIBUS always maintained the M849 shield between memory other options. The one exception was that the M8350 KA8E and M8360 KD8E external posibus interfaces were typically placed at the end of the OMNIBUS right before the terminator. The following options were introduced later, and there were many options offered by third party suppliers. -- G111 \ -- H212 > MM8EJ 8K memory -- G233 / -- M8357 -- RX8E interface to RX01/02 8" diskette drives. -- M7104 \ -- M7105 > RK8E RK05 Disk Interface -- M7106 / -- M8321 \ -- M8322 \ TM8E Magtape control for 9 track tape. -- M8323 / -- M8327 / Survival: It is still fairly common to find PDP-8/E systems on the surplus market, recently removed from service and in working condition or very close to it. A modest number are still in service doing their orignal jobs, and there is still a limited amount of commercial support from both DEC and third-party vendors. ------------------------------ Subject: What is a PDP-8/F? Date of introduction: 1972. Date of withdrawal: 1978. Technology: an OMNIBUS machine, as with the PDP-8/E. First use of a switching power supply in the PDP-8 family. Reason for introduction: The PDP-8/E had a large enough box and a large enough power supply to accomodate a large configuration. By shortening the box and putting in a small switching power supply, a lower cost OMNIBUS machine was possible. Reason for withdrawal: The PDP-8/A 800 displaced this machine, providing similar expansion capability at a lower cost. Compatability: The PDP-8/F used the PDP-8/E CPU and peripherals. Standard configuration: Identical to the PDP-8/E, except that the KC8E front anel was replaced with a KC8M front panel that had LEDs instead of incandescent lights; this front panel could also be installed on PDP-8/E systems, but the PDP-8/E front panel could not be used on a PDP-8/F because of the lack of a +8 supply for the lights. The original PDP-8/F box had a defective power supply, but a revised (slightly larger) box corrected this problem. With the dintroduction of the M8330, DEC began to require that this board be placed adjacent to the KC8x front panel, although many OMNIBUS PDP-8 systems continued to be configured (by users) with the M8330 elsewhere on the bus. As a result, the suggested order of boards on the omnibus began with: -- KC8E programmer's console (lights and switches) -- M8330 - Timing board (system clock) -- M8340 \_ optional EAE board 1 -- M8341 / optional EAE board 2 -- M8310 \_ KK8E CPU control -- M8300 / KK8E CPU registers -- M837 - Extended Memory & Time Share control Expandability: This machine could be expanded using all PDP-8/E OMNIBUS peripherals, including the external expansion chassis. The relatively small internal power supply and the lack of room for a 20 slot bus expander inside the first box were the only limitations. There were minor compatability problems with some options, for example, the power-fail auto-restart card, as originally sold, was incompatable with the PDP-8/F power supply. Survival: As with the PDP-8/E, these machines are moderately common on the surplus market, and frequently in working condition. -- 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

26 years, 8 months

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

by allisonp＠world.std.com

In late 1979 NEC sampled the 765, WD had also been building the 1793. <Sorry, I should have said that it was not readily achievable for RADIO <SHACK, not that it wasn't possible. It took RS a few more years before <they were ready to have MFM in one of their consumer level machines. No one thought it was needed. <RS's early FM had some data separation problems; I assume that that was <due to trying to keep the cost too low? they tried to cheap out and use the 1771s internal data seperation which even WD said was stupid! It was far to sensitive to bit jitter and the SA400 had really bad jitter! I used to have the test fixture and the disks to exercize them and getting an eyeball pattern on some was damm hard. It took a few oneshots and a FF package to get good data seperation. The other problem is the ribbon cable would pickup (and radiate RFI) noise like mad. If one wasn't careful there would be a ton of common mode noise on the cable too. Allison

26 years, 8 months

PDP-8/E PSU Debugging (was Q-bus pinout)

by mbg＠world.std.com

Chuck McManis <cmcmanis(a)mcmanis.com> wrote: >Megan, was that a "long" 8/e or a "short" 8/e you recovered in your haul? >If it was a long one could you take a couple of pictures of the cover for >me? What do you mean by a "long" 8/e... I thought the long box was the 8/e and the short one (what Allison has) an 8/f. I seem to remember the cover of mine has vent holes... sure, I'll take pictures of it, inside and out... maybe tomorrow. After Allison and I return from yet another trip to collect hardware... 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 | +--------------------------------+-------------------------------------+

26 years, 8 months

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

by allisonp＠world.std.com

<The RCA TV set design that RS used for a monitor for the model 1 was NOT <really adequate for 80x24 display. (YES, I've done it.) It could but the opto isolator used to keep the hot chassis and the video seperate wasn't up to the task. Bypassed and of course using an isolation transformer it was much crisper even at 80 cols. <Double density was NOT readily achievable in 1978. And the poor quality My dog, don't tell DEC that or intel. <> was SLOW. The Z-80-card in the Apple was significantly (and noticeably) <> faster. The two machines otherwise occupied about the same desk space, a Than the TRS80, every thing was faster. Next to my S100 CPM crate with a real 4mhz z80 and no wait state memory they were both slow. <> aside from the stupid, Stupid, STUPID choice to leave the Tandy machine' <> display at 16 lines of 64 characters (about half of what was on a 24x80, As it works 64wide was more useful for word processing than 32 or 40. Allison

26 years, 8 months

NEC APC III

by roblwill＠usaor.net

-----Original Message----- From: Fred Cisin (XenoSoft) <cisin(a)xenosoft.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Friday, April 09, 1999 1:51 PM Subject: Re: NEC APC III >With a few exceptions (and I doubt that the APC III would be one of the >exceptions), the 720K 3.5" can simply be cabled to replace the 720K 5.25". >The original design of it was intended to permit that. > Probably not. > >But that doesn't solve your need for a boot disk. In an earlier message, >you mentioned that your current boot disk is "Stoned". If so, a bit of >work with a sector editor might fix it. > Yeah - it's got the "Stoned" virus on it ( I think >Try to resurrect the 2.11 boot disk that you have. It's the HD - I can't access it - it starts to boot, says "MS-DOS 2.11", then comes up with an error (can't remember what, and the computer is at my school), and locks. -- -Jason Willgruber (roblwill(a)usaor.net) ICQ#: 1730318 <http://members.tripod.com/general_1> >MS-DOS 2.11 was the version that MICROS~1 provided for companies that >needed/wanted to customize for special hardware, such as 720K drives. >PC-DOS didn't support 720K until 3.20. >Previously (MS-DOS 2.00), sometimes only MODE.COM, and sometimes >FORMAT.COM, varied from one brand of machine to another. >But in 2.11, IO.SYS might be significantly altered. > >

26 years, 8 months

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

by edick＠idcomm.com

please see imbedded comments below. Dick -----Original Message----- From: allisonp(a)world.std.com <allisonp(a)world.std.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Friday, April 09, 1999 7:18 AM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 51/4 floppies) >On Fri, 9 Apr 1999, Richard Erlacher wrote: > >> 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! > >It was done though. The 6845 you generally talk to it's local ram through >it not around it. The H19 terminal did the latter. It was, indeed, but not when the Apple was designed, since the 6845 and 6545 didn't yet exist. >> 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. > >It proved software was more important than hardware. The best cpu with no >software was still nothing. The z80 was maybe the best at the moment but >the 6502 was as versitile and plenty fast enough to make up for it's >limitations. There were many people who disagreed with that performance comparison. The two processors (I used them both extensively) were different enough that comparison and contrast was not easy. The Z-80 had many registers and a rich instruction set of which much was awkward and difficult to use. The 6502 had fewer registers and fewer instructions but they were amplified by addressing modes not readily available to the Z-80 user, particularly if his code was for CP/M which sort-of required you stick to the 8080-compatible instruction subset. The fastest 6502 available in 1980 was a 4 MHz processor which stroked memory for 125 ns almost every cycle in its typical application. The Z-80 had just that year become available in a "B" version (6 MHz) which stroked memory for slightly less than 3 clock ticks on a memory cycle and barely 1 (166 ns) on an unmodified M1 cycle. Having said that, and given (1) that the two processors executed code at about the same rate for the same memory cycle length (hard to prove or disprove) and (2) memory cost was more of an issue than system performance, hence the memory cost was used to set the rate at which the CPU operated, I'd say there's really no basis for comparing the actual performance of the two processors. >Likewise the trs 80 would prove lowercase and some more speed were very >desireable (based on the two most common mods!). The TRS-80 could have been put out with (1) an 80x24 display rather than the 16x64, it could have solidly supported double-density FD's (in the model 3) and it could have operated at about 4MHz rather than the 2.-something it used, and it could have switched in and out the ROM so it could run CP/M but for the greed of Tandy Corp. It would have cost them an additional $5 and change to put those features in their model 3, but they thought "well, we're going to sell a million of these . . . " and decided they preferred having the dollars. Had they gone the other way, they probably would have had the "personal computer" market all to themselves. They had a huge distribution network, a huge sales force, a huge service network, unlike any other microcomputer manufacturer of the time. Within a year, Apple owned the personal computer market, particularly with respect to businesses, even though Radio Shack had better packaging by the time the Model 3 came out. That was also about the time it became common to see the 80x24 displays, the 8"disk drives, the nearly 4MHz Z-80 running CP/M, the extra 16K memory, etc. on the Apple II. If Tandy had gone with the better design, which was on the table, there probably would be no IBM PC today. >Allison > >

26 years, 8 months

PDP-8/E PSU Debugging (was Q-bus pinout)

by allisonp＠world.std.com

<On another tack, the chassis I got did not come with any covers. I don't <know if this is "standard" or not. (I know the PDP-5 isn't designed to be They are missing then. The 8E had a cover as did the 8l and I think the 8I. <and so that has left me curious. I'm probably going to build a display rac <for it anyway with clear sides so that folks can "see" the innards without <risking getting fingers in them. Compare to a real top for vent slots as needed. <P.S. I'd like to thank Allison for relating the story of bringing up her <8/F since it inspired me to move forward on this project (code named <"FrankenEight" as it is a PDP-8 built out of parts exhumed from dead 8's o <other mysterious sources ...) My pleasure. I'm still working on mine to get it talking over the serial (I havent tried and I have to make a RS232 cable). Still they are a really fun machine and gobs of fun to hack new interfaces only. Omnibus 8s were the most hacked of the series as the bus made them easy to interface to and DEC make no secret of what is needed to do it. add to that with 8kw or more of core it's a machine that can do serious work if one chooses. Allison

26 years, 8 months

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

by CLASSICCMP＠trailing-edge.COM

>On Thu, 8 Apr 1999 CLASSICCMP(a)trailing-edge.com wrote: >>I suspect when you say "MFM" you mean "all the soft-sectored data storage >>schemes descended from the original IBM 3740 (FM) standard", in which case >>you're right. >So, does that mean that those quarter-track schemes used for copy >protection on the Apple II could also be implemented on a PC or >Macintosh disk? The reason why I ask is because I've never heard of such a >practice. I think my statement is entirely unrelated to your question. The Apple ][ DOS 3.2/3.3 sector format, while it follows conceptually the same ideas as the IBM 3740 standard in that they are both ways of recording blocks of data on floppy disks and both encode the track and sector number in the header, is not by any stretch compatible with it. On an Apple Disk ][, you have complete control over the stepper phases, so quarter- and half-tracking is possible. (You can also blow out the Apple's power supply by switching the phases on and off at a certain "bad" rate, too!) The 34-pin Shugart SA400-style interface used for floppies in PC's doesn't allow half- or quarter-track stepping, though you could imagine trying to read or write something while rapidly stepping in/stepping out. If you want more information, I highly recommend that you read the Shugart SA400 interface documents, or the interface documents of a drive with a similar interface (i.e. the TEAC datasheets, which are also very complete.) I don't know of any documentation of the Macintosh 3.5" floppy interface. If someone could point me towards the relevant documents (or even the part numbers they claim to describe) I'd be quite happy! -- 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

26 years, 8 months

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

by allisonp＠world.std.com

<I grew up on the Z80, and for a time I thought that the 6502 was a Same here. <horrible little chip. But then I got to use a 6502 in the BBC micro and I I didn't have that opinion. It took a bit of getting used to having 256 registers that happen to be in the base memory page though. ;) totally revised my opinion of it. The 6502 instruction set was simple and <fairly clean. For high-level languages it was a fine processor (BBC basic <on a 2MHz 6502 was faster than similar BASICs on 4MHz Z80 machines). In the speed race they were close enough that how an app was structured and written had a greater effect. <No. Never forget the 3 magic letters 'IBM'. That's why the PC was <succesful. Technically there were plenty of better machines around at the <time, but they didn't have the appeal of coming from a company that <_every_ computer centre and DP manager had heard of. That is a fact! IBM legitimized the desktop machine even if it was inferior design. Allison

26 years, 8 months

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

by CLASSICCMP＠trailing-edge.com

::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? I suspect when you say "MFM" you mean "all the soft-sectored data storage schemes descended from the original IBM 3740 (FM) standard", in which case you're right. There are a few oddball hard-sectored drives that don't have any header at all on the data in each sector - hardware counters in the drive controller keep track of this stuff. Of course, once your head stepper starts stalling or your index sensor gets dusty, all sorts of nasty things happen with this scheme. And, even more rare, are some embedded-servo floppy disk systems where the location on disk is encoded in special formatting that cannot, in any reasonable way, be called a "sector header". -- 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

26 years, 8 months

[OT] <10 yo DG Aviion

by jeff.kaneko＠juno.com

Try the Newsgroup: comp.sys.m88k Good Luck! (You're gonna need it!) On Fri, 9 Apr 1999 15:50:45 -0500 "David Williams" <dlw(a)trailingedge.com> writes: >I know this system isn't 10 years old yet, but a company I use to >work for gave me a 88000 based Data General Aviion. I believe it is >an AV 4625 model if I'm reading the back right. DG's site only >talks about P-II and P-III based Aviions with nothing about the >earlier 88000 based ones. Anyone have any web site pointers or >info on these for me? I'm currently hitting each of the main search >sites without much luck. > >Thanks. > > >----- >David Williams - Computer Packrat >dlw(a)trailingedge.com >http://www.trailingedge.com ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]

26 years, 8 months

[RANTISH] Programming Stupidity

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

> From: Daniel A. Seagraves <DSEAGRAV(a)toad.xkl.com> > To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> > Subject: [RANTISH] Programming Stupidity > Date: Friday, April 09, 1999 10:15 > > > [Large progressive rant here, nevermind me...] First of several <snips> in this msg... >You guys think BASIC is bad? How about BASIC that automagically > writes bad Windows code for you! Sounds about right. Never tried VB myself, (well the beer, yes, that's ok) I have an assistant who is somewhat interested in using VB for righting apps. I had occasion to write a little PLC emulation for a dos box to replace a failing (and not Y2K compliant to boot) PLC that rings the bells at the school to announce change of class, lunch etc. It also controls the sprinkler system. Anyway, a couple days hacking around in Turbo Pascal 6 produced a simple little program that controls a few external devices on a time schedule via a $2 interface connected to the printer port. Runs on XT's and up, around 23k for the .exe file. Works fine. Just a text file with the schedule info in it. Too easy. My assistant thought that was ok, so he thought he'd try it in VB just as an exercise. At last count, it was something like a 650k exe file, needed at least 4 mb of ram, and he still hadn't found a way to get control over the bits in the printer port to let it actually do something useful!! He's still nibbling away at it, he's perssistant, so he'll probably make it go. Eventually. Been 6 weeks now though..... > This thing couldn't make optimized code > if Billy-boy's monopoly depended on it. Pity it doesn't depend on it. > On top of that, the bad code that it DOES generate doesn't even work. > We build the .EXE on a Win98 machine - Now it refusues to run on 95. Micro$oft producing non backward compatible software? Nah, couldn't believe that.... yeah, right. > Microsoft's wizard for making install programs for your software sucks worse. > It replaced some DLLs it wasn't supposed to have on our (one and only, thank > Goddess!) NT server, and NT crashed like you wouldn't believe. Oh yes I would. I just drop kicked the last of our NT servers. 2 years of tinkering and updateing and god knows what else and it STILL kept screwing up a database. It's now my workstation. Running 98. The family resemblance is still a pain at times, but at least it only gives ME trouble, not half the darn school.. > I'm gonna have a hell of a time putting THAT back together.. Doesn't sound like a fun weekend project. Best of luck. You'll need it. . On top of this, the > installer doesn't run under 95, either. It starts just fine, makes a pathetic > attempt at copying files, then blows up horrbibly with Error 0x16E. Wasn't > Billy saying they were supposed to make our error messages make SENSE? To Micro$oft Tech staff when you ring them at $25 a problem maybe. But I wouldn't even count on that. > an error message like that, a dialog box reading "YOU LOSE!" would be better. You've already lost if you have to run Windoze whatever. I'd switch to something more stable in a minute, but the sad part is that Windoze is everywhere, so we have to teach our students to use it and the apps that run on it, because that's what they will likely find in the real world.. > Another quote from my boss: > "In programming, it doesn't matter how well it runs or does it's job. The > bottom line is, 'can we sell it to someone?'" What planet is this guy from? Originally? Marketdroidia? He sounds like one of those funny creatures. > Is it just me, or is that just plain wrong? Please say it's not only me... It isn't only you. I think you have a couple of million mates globally. Minimum. Trust me on this. > I hate being alone, 'cause that means I'm right and everyone else is wrong. You are in absolutely no danger of that. Micro$loth bashing may become the all time greatest user participation sport of the 21st century. > Sorry for that, I just needed to vent. Do with it what you will... Just confirms much I already believed..... Cheers Geoff Roberts VK5KDR Computer Systems Manager Saint Marks College Port Pirie, South Australia geoffrob(a)stmarks.pp.catholic.edu.au

26 years, 8 months

Abort, Retry, Ignore, Fail? (Was: stepping machanism

by ethan_dicks＠yahoo.com

--- Sean 'Captain Napalm' Conner <spc(a)armigeron.com> wrote: > Oh. You're one of *those* ... okay. > > -spc (Hate Perl ... okay, so I'm a bit of a language snob 8-) I am presently paying for my classic computer hobby by crafting perl for 50+ hours per week at consultant's wages. I *love* perl! -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

26 years, 8 months

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

by fpp＠concentric.net

> Yes, that's true, but, the 4MHz+ (4.9152 MHz, actually) Z-80B with 64K of > RAM, a 24x80-charcter display, double-density diskette interface that > actually worked, built-in capability to install a hard disk, AND the ability > to run CP/M right out of the box, in 1978-1979 e.g. at the fall '78 COMDEX, > which was BEFORE there were "Over 10,000 programs written for the Apple" Would be a good argument but; Comdex did not exist 1978. There was The West Coast Computer Faire (San Jose, CA), or NCC show (Anaheim, CA I believe in 79) mostly heavy iron.

26 years, 8 months

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

by edick＠idcomm.com

You're right in that it would be silly to bang the head assembly into anything. I didn't say they did that, though it would work for a while, maybe. It's clear to me that Apple drives do things differently from other drives just from listening to them when the machine starts up. I'd never pretend to "know" what they do. In fact I'd be hesitant to admit it if I did know. Your observation that there were alignment problems with Apple disk drives sounds familiar too. Could it be that they actually did bang the head into the stops? My contempt for Apple begins and ends with their total disregard for the value of your data. If you wrote to their floppies, especially if your computer was in the "front room" of a business, exposed to whatever dust was carried in by customers and wind, etc, from the parking lot, (I had a client years ago, whose mail-order business was operated with the "help" of an Apple-II with two controllers and three drives in just such a location.) you'd frequently observe the computer locking up because it had come to a bit it couldn't read. The reason was probably contamination of media or drives, but the only recovery was the reset. Your data, meanwhile, and perhaps your customer calling long distance, were gone by now. They designed the MAC with no memory parity assuming that you'd not mind if your data was corrupted without your knowledge, and though the disk handling was a bit more mature than the Apple-II "I give up . . . and die" it wasn't much better. I've never taken note of the 8" drives' sensor for track 43. I always believed that since they had provided a "low-current" control on the interface cable, it was not necessary. I suppose I'd have taken note if one had failed along the way. Of the many dozens of 8" drives I've owned, I never had one fail. I used several of these for 7 or 8 years, moving them about and just generally abusing them, yet they seemed to keep going. I only occasionally aligned a drive for someone else, or as part of a checkout of an "experienced" set of drives we were buying. The only drives which ever gave a noticeable amount of trouble were the Persci. They were "hangar queens" of the first order. I had a couple of those for a time because I had to verify they worked properly with our controllers. 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 8:50 PM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 5 1/4 floppies) >> >> 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 > >A very silly nitpick: > >I have an 8" drive here with 2 slotted optoswitches on the head carriage. >One is on track 0. The other is on track43 and all later tracks. The >reason for the latter one? It automatically does the write current switch >at track 43. > >> minimim number of wires and signals possible and made up the difference >> with software, rather clever in my mind. > >And rather silly in my mind. Continually banging the head into the end >stop does cause the alignment to drift. I've had plenty of Disk IIs and >1541s (another drive that seems to bang the head rather too much) in for >repair. Often alignment is the problem. > >> >> Allison >> >> >> > >-tony >

26 years, 8 months

OT: Microsoft, again!

by rigdonj＠intellistar.net

>Subject: Microsoft, again! >Date: Fri, 9 Apr 1999 15:23:12 -0400 > >Bucks For Bugs >By Randy Whitted, TechWeb contributor > >Microsoft is setting a dangerous precedent by announcing the next Windows 98 >"service pack" -- read: bug fix release -- will cost users $89. > >What we're seeing here is the first instance in the software industry of a >company charging a significant sum to, hopefully, improve a product that >didn't work right in the first place. > >As much as I'd like to deny it, what Apple, and even Linux developers, do to >innovate in the software industry pales in comparison to the big Kahuna. >Microsoft sets the status quo, which is why watching its moves, even if >we're not customers, is wise. > >While I'm not privy to Microsoft's motives, I can guess the company's >thinking goes something like this: "We spent a good deal of time and money >fixing these problems, and we want to be compensated for our efforts." PC >users should then say, "We spent a good deal of money on your product, which >didn't work as you said it would, and we'd like the thing to work right at >your expense." > >But here's the catch: Did Microsoft promise to deliver a version of Win 98 >that would be bug-free? Do any software developers say they release bug-free >software? Of course not. They know, as do consumers, that software will >always have problems, glitches, performance issues, and some bugs. No one is >immune from releasing buggy software. It's a fact of life. > >However, how a company deals with its bugs is the true test of a winner or >loser. And quite simply, charging users for a bug fix is a dumb move. > >Imagine if Apple tried to pull this off. There would be a mass defection, >public scrutiny, a stock price plunge, and enough ridicule to ruin >everything the iMac accomplished. > >That is why Apple, shortly after confirming bugs in Mac OS 8.5.1, released a >bug-fix patch that could be download for free. Those fixes were subsequently >incorporated into later shipments of 8.5 -- it's called slip-streaming. > >It should be noted, however, that Apple's forthcoming Veronica -- Mac OS 8.6 >-- is not a bug fix. Sure, it includes several bug fixes, some new drivers, >and enhancements, but it is an updated version of the operating system that >also offers new features and functions. Because it is an upgrade, Apple is >not charging full price. Mac OS 8.6 is expected to be free for recent 8.5 >buyers, cost about $20 for a CD, and free when downloaded from the Internet. > >So, perhaps Microsoft, in its clumsy way, is just putting the wrong spin on >this whole service-pack issue. My advice is the company should call it >"Windows April 98," ship it in August, and tout the release as having >several performance enhancements instead of just bug fixes. At least the >consumer could imagine for their $89, Windows was working better than >before, instead of simply working the way it should have been in the first >place. > >The implications of letting Microsoft get away with this could be >significant for the sectors of the software industry in which there is still >competition. To me, Microsoft is saying it still doesn't believe there is >any alternative to Windows, and as the dominant OS provider, whatever its >says goes. Consumers, the ball is in your court. Linux is free. The Mac OS >is polished and ready. Make your move. > >Randy Whitted is a copy writer/technical adviser at Studeo, a marketing and >communications agency in Provo, Utah. The opinions expressed here are >strictly his own. > >http://www.techweb.com/ <http://www.techweb.com/> > > http://img.cmpnet.com/tw/newsletters/blank.gif ><http://img.cmpnet.com/tw/newsletters/blank.gif> >http://img.cmpnet.com/tw/newsletters/blank.gif ><http://img.cmpnet.com/tw/newsletters/blank.gif> >http://img.cmpnet.com/tw/newsletters/blank.gif ><http://img.cmpnet.com/tw/newsletters/blank.gif> > http://img.cmpnet.com/tw/newsletters/scoop-bottom.gif ><http://img.cmpnet.com/tw/newsletters/scoop-bottom.gif> > http://img.cmpnet.com/tw/newsletters/arrowright-gray.gif ><http://img.cmpnet.com/tw/newsletters/arrowright-gray.gif> ><http://www.techweb.com?ls=twb_ibd> http://www.techweb.com >

26 years, 8 months

Thoughts on Taking Inventory

by kees.stravers＠iae.nl

On Sun, 28 Feb 1999 21:56:42 -0500, mbg(a)world.std.com (Megan) said: >>I'd also have a "shadow" page that showed the outlines of the "standard" >>bus types so that boards could be identified by their outline. > >Kind of line the charts 'plane-spotters' used... > >I'll go that one better... I've been thinking of taking pictures (now >that I have a digital camera) of one each of all the qbus boards I >have in my stock, so that people can see what they look like. [This reaction is a bit late, I'm slowly catching up on my classiccmp reading] I think this is an excellent idea! It can even be done without a digital camera for the dual- and quad wide boards, just lay them face-down on a flatbed scanner! This is a lot quicker and the resulting images look just fine. I did this for the images of the RQDX boards on my RQDX page at <http://www.vaxarchive.org/hw/rqdx/> You can see that the boards look great in the images. (Click on the small images to see larger ones.) If you have the time to scan the boards, but not the room on your web page to post them, I can store them on VAXarchive. In fact, if everyone that has a few DEC boards lying about, would scan them and email me the resulting JPG's, I would have a 'visual field guide' online in no time :) Kees. -- Kees Stravers - Geldrop, The Netherlands - kees.stravers(a)iae.nl http://www.iae.nl/users/pb0aia/ I'm Sysadmin and DEC PDP/VAX preservationist - Visit VAXarchive! http://www.vaxarchive.org/ (primary) http://www.sevensages.org/vax/ (mirror) http://www.coyote.org/mirrors/vaxarchive/ (mirror)

26 years, 8 months

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

by edick＠idcomm.com

In the late '70's, I think the microcomputer market was highly simplistic with respect to what it is today. Take a look at the comments I've imbedded in your text below. Dick -----Original Message----- From: Sellam Ismail <dastar(a)ncal.verio.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Friday, April 09, 1999 12:58 PM Subject: Re: stepping machanism of Apple Disk ][ drive (was Re: Heatkit 51/4floppies) >On Fri, 9 Apr 1999, Richard Erlacher wrote: > >> The TRS-80 could have been put out with (1) an 80x24 display rather than the <snip> >> If Tandy had gone with the better design, which was on the >> table, there probably would be no IBM PC today. > >This is a highly simplistic view of the early home computer market. He >with the biggest dick didn't always go home with the babe. There was much >more to the computer to entice someone to buy it than just the speed of >the microprocessor. Available software and overall marketing effort >played the bigger role, and Apple exploited this by advertising the figure >of "Over 10,000 programs written for the Apple". Yes, that's true, but, the 4MHz+ (4.9152 MHz, actually) Z-80B with 64K of RAM, a 24x80-charcter display, double-density diskette interface that actually worked, built-in capability to install a hard disk, AND the ability to run CP/M right out of the box, in 1978-1979 e.g. at the fall '78 COMDEX, which was BEFORE there were "Over 10,000 programs written for the Apple" would have been hard to beat . . . particularly under the aegis of a nation-wide company with these facilities under one management already in place. Remember APPLE had to rely on small-time stores like Computerland for distribution, and their service, mostly indirect, was slow and costly. The things which seemed to make the Apple fit the business model the best (before Visicalc) was the 24x80-character display and the 8" diskette drives sitting next to it. With the aid of the Videx video display adapter and the Sorrento Valley Associates' 8" disk drive interface, the machine suddenly began to look like what people had come to expect when they learned about computers and how to use them. It's true that "He with the biggest dick didn't always go home with the babe" but you mustn't forget that in this case, the dick was overtly measured and advertised. Whereas the above described TRS80-III wouldn't have been the fastest on the market, it had the packaging and the ability to turn into much more computer for much less money than the Apple, though with the gradually and later not so gradual increase in Apple's market share, they were able to become somewhat more competitive in spite of the high cost of distribution and service. The way it turned out, Tandy Corp ended up with precisely the smallest, didn't it? A barely-over 2MHz processor which stroked memory more at about 1.5 microsecond per memory cycle??? It was obvious to everyone who used the Radio Shack model III that their computer was SLOW. The Z-80-card in the Apple was significantly (and noticeably) faster. The two machines otherwise occupied about the same desk space, and, aside from the stupid, Stupid, STUPID choice to leave the Tandy machine's display at 16 lines of 64 characters (about half of what was on a 24x80, and about what was on an Apple with the standard display), they were quite similar. Of course the Radio Shack machine was SLOW . . . >As far as a comparison between the 6502 and Z80, its been argued over time >and again, but the consensus is generally that each processor could >perform some task faster than the other, and overall, applications running >on both seemed to perform equally. Of course, when you involved >subsystems like disk access, the Apple tended to have an advantage over >some Z-80 systems (and even other 6502 systems). I don't know that the assertions you make here are correct, but I don't believe they're completely off-base. It's important to remember that if one computer is not at least ~2x the speed of another, most tasks will seemingly execute in more or less the same time as observed by a user at the console. If two are set side-by-side and compared, the difference in performance seldom amounts to the ratio of the clock speed or the ratio of the memory access time. Often the result is totally counterintuitive. (Meaning something's been overlooked!) Most of the time, it makes little difference. Whether it takes four hours or six to handle the weekly payroll doesn't matter very much if it's run at night. >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] >

26 years, 8 months

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