test-drb April 1999

test-drb@ccmp.vtda.org

170 participants
1190 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

25 years, 9 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

25 years, 9 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

25 years, 9 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.

25 years, 9 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

25 years, 9 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

25 years, 9 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

25 years, 9 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

25 years, 9 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

25 years, 9 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 | +--------------------------------+-------------------------------------+

25 years, 9 months

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test-drb April 1999