Any "old tech" gurus recognize this?

Had one of these way back in the day. This is only part of it. Whole thing took up (3) 6ft 19" racks, required 208/240V. Kept the room warm on cold winter days, LoL. Had a blast using it, but its days were numbered. Cost a small fortune back when. I made decent living working on them and similar pieces of equipment. Gotta have some grey hair to remember these... Cleaning out 5 decades of my electronics collection (which the wife does not understand), ran across lots of old memories... and some stuff I don't recall what it is, where I got it, or why. Aging is such fun.
So, trivia question for the day - what was this and when was it in common use? NO GOOGLING Yes, I actually used this machine and others like it - back when things were made to be serviced, not tossed out.

Yup, used one back in 1979, Digital Equipment Corporation (DEC) PDP-11/40

That's a newer one . I go back to the original PDP-8. I remember that a 4k x 12 -bit memory bank cost $10k. The ASR-33 kept wearing out, and the ASR-35 did a lot better. Adding the high-speed paper tape reader/punch was a huge step up, only 2nd to the 32K word disk drive that also cost about $10k. I could enter the RIM loader in about 5 seconds flat. Muscle memory. I did repairs to the component level. The most common failure was a cheap germanium diode. There were about 3 ICs in the whole machine.

I figured there might be a few of us still alive and kicking with real hardware experience...
Never worked on a PDP/8, but scrapped one for parts back in the 90s. Still got the front panel somewhere.. why I don't know
Bought my PDP11/40 when I was in college in early 80s..working as an E tech, so had access to too many gadgets that cost way too much of my income. My 11/40 had 3 "disc drives", IE a 19" rack, each drive weighed around 90 lbs, used over 500W, and gave a whopping 2.5MW (mega word, 18 bit) storage... yes, a whopping 5 MB storage, and needed "only" 1500W to run it.. Upgraded to 256MB solid state RAM, hung a Decwriter LA36 on it, and thought it was the cat's meow. Didn't want a paper tape reader, and I had all I wanted from punchcards... happy to have those huge disc drives. Especially fun to put them in diagnostic mode, seek test, and watch the room lights flicker as the 19" rack would try to walk across the floor like a washing machine with out of balance load of clothes. OK, I was easily amused... Somewhere I still have a core memory board... that was a wild concept back then. Then SRAM came along, and core memory became instant dinosaur, like so many other "state of the art" technologies.

Also had a Data General Nova 3. Liked that machine too, similar specs to the DG PDP. Most common problem I ran into was blown RS232/485 line driver chips/transistors due to line transients, or more likely someone hot-plugging a terminal. Yep, everything was repaired at the component level. Didn't toss a board just because it quit.. A typical mini mainframe board cost more than most cars then, so you had to fix it unless it was beyond repair. Got out of the computer repair biz when it all went throw-away. Companies didn't want to pay for skilled techs, just hire kids, give them a cheat-sheet to pull-n-swap boards, and call the board swappers technicians. My view was, if you didn't know what was happening at the chip (if not the gate) level, you weren't a tech, but a swapper. Now we don't fix anything, not sure it's even possible. I couldn't even see components today, if I could even find parts and had the surface mount soldering equipment. Not worth the effort. Computers are toasters. Toss and buy another. Programmed on a DE VAX, but never owned one. Tried a MicroVax (that was back when the word "VAX" had a completely different meaning!!), but got into VME bus MC68K machines and never looked back. Still have some old MC680X0 based machines, and they still work perfectly. Ran unix and microware OS9, loved it. Best machines I ever used.
Those were the days. Got paid to have fun, working on and using machines I actually enjoyed. But it is mind boggling that the little Raspberry Pi4 that fits inside my palm has far more power than all of the old equipment I had/worked on - put together. Back then, that was SciFi that even I didn't think would ever happen. Go from a room full of mainframe eqpmt weighing tons and using tens of KWs to a device the size of a deck of cards using a few watts, and orders of magnitude more powerful. Guess it's just that much more amazing when you have enough gray hair to remember from whence we came.

Try convincing a gen-z youngster that computers used to require toggling in bootloader on the front panel before it would do anything, and output was on a line printer termial or RS232 terminal. They look at you like you're from Mars, no clue. Comms were over dedicated current loop lines, or later over local RS232/485, and external distant IO was done via a 150 or 300 baud (yes, 300 bps!!!) modem. Today, they get cranky when their internet connection slows to a measly 100 mb/s...
photo - sad remains of my old DG Nova 3, front panel, been buried in a box of parts for decades

Found front panel bezel for the old PDP8, all I have left of it...
Also, 2 working AMD 2900 single board microprocessor trainer boards... Guessing they don't teach CPU register level arithmetic functions in school anymore.
There was something about single stepping a CPU through machine code, watching the address & data bus change - hopefully as expected. You learn to appreciate (or hate) CPU instruction sets & functions (depending on the CPU), when you're coding in assembler. Lost concept today.

This one was very cool .. lights and all ..

"A CM-5 was the fastest computer in the world in 1993 according to the TOP500 list, running 1024 cores with Rpeak of 131.0 GFLOPS, and for several years many of the top 10 fastest computers were CM-5s."

Worked as a Software Test Engineer, using GenRad 1797 functional testers and 2270 in-circuit testers that contained PDPs. We created programs (pushing 1's and 0's around) to test out circuit boards. We had a paper writer/reader that was used for backup and also fixed-removable disks. It was great when we finally got a 300MB fixed disk (about the size of a wash machine) to store out backups to get rid of the tape backup process.

I remember my Digital Circuits professor getting his hands on a IMSAI 8080 microcomputer kit and putting it together, he was giddy!

concord said:

Worked as a Software Test Engineer, using GenRad 1797 functional testers and 2270 in-circuit testers that contained PDPs. We created programs (pushing 1's and 0's around) to test out circuit boards. We had a paper writer/reader that was used for backup and also fixed-removable disks. It was great when we finally got a 300MB fixed disk (about the size of a wash machine) to store out backups to get rid of the tape backup process.

I remember my Digital Circuits professor getting his hands on a IMSAI 8080 microcomputer kit and putting it together, he was giddy!

IMSAI 8080 - Wikipedia

en.wikipedia.org

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Wow, that brings back forgotten memories! When I was freshman in college, the university had an Imsai 8080.. they couldn't get it to work; had some hardware problems, so it was shelved. Naturally I found it, asked if I could work on it, and since nobody else was interested, they said go ahead. Got it running, upgraded it a bit, and used it for data sampling/logging in our physics lab. Wasn't exactly powerful even back then, but man was it fun. I learned a lot from that machine... including that I didn't care much for the 808X instruction set... After learning Dec PDP, VAX, DG Nova 3&4, MC68XX & 680X0 architecture, 808X just didn't cut it for me. But, I found a Z80 CPU board for the Imsai, and it was a bit more tolerable. Still, a fun machine to learn, like so many were back then.. when you could see and actually do something "under the hood".

808x architecture and instruction set wasn't the best one around, but Intel had the best marketing to seal the deal with IBM. Ditto with MS-DOS. And the rest is history.

I had the engineering college's PDP-8 all to myself for 3 years. In the beginning my entire computer background was a Fortran class using the IBM 1620. There was one soon-to-depart grad student who knew how to run the PDP-8 and he mentored me with running it and assembly language. Once he was gone, I was the only student who knew how to do anything with it. There were no classes that used it, and none of the profs had a clue. This was in 1968. It had 8k memory, A-D, D-A, Calcomp plotter, and the oscilloscope peripheral. Later, added high speed paper tape and the 32K fixed platter disk. I soaked it up quickly, largely because of FOCAL, similar to BASIC but much, much nicer. Did the PDP-11 have FOCAL? Other than both being stored program/Von Neumann machines, the PDP-8 and PDP-11 were hugely different, I don't know if DEC invented any of it, but the variable length instructions, operand tag fields, and memory-mapped I/O made the PDP-11 feel like a luxury car compared to the moped-like PDP-8. I wish the architecture had survived, but once the IBM-PC came out, the die was cast.

I want to tell one story. The engineering school had a full time tech (a good guy) to keep all the lab equipment running. He was given the job to rearrange the PDP-8 equipment racks to add a new peripheral. The I/O bus was a daisy-chain with 6 cables in and out of each peripheral. I happened by shortly after he started the job, while he was carefully labeling each cable and recording where it went from and to. I volunteered to help and just pulled out all of the I/O cables and made a heap of them on the floor. Probably about 30 of them. I'll never forget the look of horror on his face while I was doing this. He didn't know that all of the cables are identical except for length, and once you know how the I/O bus works, it's easy to put it back together. No harder than running a bunch of cables from a switch to a bunch of cameras, except these were a good half inch in diameter. On later models the I/O cables terminated on double-sided PC boards and the cable count went from 6 to 3.

tigerwillow1 said:

808x architecture and instruction set wasn't the best one around, but Intel had the best marketing to seal the deal with IBM. Ditto with MS-DOS. And the rest is history.

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Yes indeed, that is definitely true. Always said, if programmers (real ones, back before code generators and AI) had to program in assembler for 2 years before being allowed to write high level code, the landscape would look entirely different today. But, marketing and low initial cost always wins in the long run - regardless of long term costs or problems. People have short memories when something is cheap.

After college I went to TI. They had 2 conventional microcomputer models, the 960 and 980. I was then able to be a small part of the new 990 development and it became my very favorite architecture and instruction set. Similar in many ways to the PDP-11. It was so darn easy to program in assembler that high level languages were pretty useless to me. Too bad that this one didn't go into the IBM-PC. TI was a semiconductor manufacturer and defense contractor, and didn't know how to market computer equipment. Later at Intel I wasn't part of the 80286 development team but had the opportunity to review its spec, and thought its method of addressing more than a megabyte was horrible and unworkable. IBM committed to using the 286 with OS/2. I was stuck working on both of them for a couple of years. They both went down in flames pretty quickly and the computer world was saved with the 80386 that had a decent addressing mechanism instead of 80286 protected mode.

Oldtechguy66 said:

Yes indeed, that is definitely true. Always said, if programmers (real ones, back before code generators and AI) had to program in assembler for 2 years before being allowed to write high level code, the landscape would look entirely different today. But, marketing and low initial cost always wins in the long run - regardless of long term costs or problems. People have short memories when something is cheap.

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Oh no way we would have computer programming students learn assembly now .. the entire discussions of big or little Indians would offend them and they would need to seek refuge in a safe space ...

tigerwillow1 said:

I had the engineering college's PDP-8 all to myself for 3 years. In the beginning my entire computer background was a Fortran class using the IBM 1620. There was one soon-to-depart grad student who knew how to run the PDP-8 and he mentored me with running it and assembly language. Once he was gone, I was the only student who knew how to do anything with it. There were no classes that used it, and none of the profs had a clue. This was in 1968. It had 8k memory, A-D, D-A, Calcomp plotter, and the oscilloscope peripheral. Later, added high speed paper tape and the 32K fixed platter disk. I soaked it up quickly, largely because of FOCAL, similar to BASIC but much, much nicer. Did the PDP-11 have FOCAL? Other than both being stored program machines, the PDP-8 and PDP-11 were hugely different, I don't know if DEC invented any of it, but the variable length instructions, operand tag fields, and memory-mapped I/O made the PDP-11 feel like a luxury car compared to the moped-like PDP-8. I wish the architecture had survived, but once the IBM-PC came out, the die was cast.

I want to tell one story. The engineering school had a full time tech (a good guy) to keep all the lab equipment running. He was given the job to rearrange the PDP-8 equipment racks to add a new peripheral. The I/O bus was a daisy-chain with 6 cables in and out of each peripheral. I happened by shortly after he started the job, while he was carefully labeling each cable and recording where it went from and to. I volunteered to help and just pulled out all of the I/O cables and made a heap of them on the floor. Probably about 30 of them. I'll never forget the look of horror on his face while I was doing this. He didn't know that all of the cables are identical except for length, and once you know how the I/O bus works, it's easy to put it back together. No harder than running a bunch of cables from a switch to a bunch of cameras, except these were a good half inch in diameter. On later models the I/O cables terminated on double-sided PC boards and the cable count went from 6 to 3.

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Now that you mention it, I do believe our school's PDP11/40 had Focal available, as well as COBOL, FORTRAN, and BASIC. Being a C-Sci/engineering major, Fortran was the only thing that interested me (aside from assembler). Never got to play with the PDP8... only models I saw belonged to a mainframe field service engineer friend I was working for.. he had several, but were already obsolete, so we scrapped them for parts. The university replaced the PDP11/40s with VAX 750, then 780. What a difference. I loved the VAX architecture. It was slick and well thought out. A pleasure to program low level. Later, I discovered the MC68K CPUs, which were very similar to the DEC VAX architecture... memory mapped IO, PIC code, re-entrant, easily ROMmable, auto increment/decrement, true asynch interrupt driven IO stack as well as polled, and a nice orthogonal instruction set. But overall, I'd have to rate the DEC VAX series as one of my all time favs for programming - but never owned one. I ended up with the PDP11/40 and multiple peripherals from a surplus sale. Managed to put it all together and get it working. It was a learning maching for me, and a lot of fun as well. Not too many college kids had mini mainframes in their living rooms I guess... seemed perfectly normal to me

Wow, forgot about the TI 9XX series. Limited exposure to them, all surplus stuff I ran into later one. TI had a HUGE plant up in Johnson CIty TN (about 90 min from me), if I recall. Big employer in the region back then. Used a good bit of TI components in my E/T jobs, but never had anything based on the 990 that I recall. I do recall studying it. Advanced for the day.
Oh yes, the 80286 and paged 1M memory segments (640k really). Never liked segmented/paged memory. Straight, linear, contiguous was to my liking, w/memory mapped IO. Much simpler and more efficient from multiple standpoints. But, segmented stuff was everywhere, cheap to make; so became dominant.
When the RISC stuff came along, guess I lost interest. Instruction sets were going backwards (simpler and less powerful), but faster execution supposed to make up for additional code needed for a truncated instruction set. Didn't seem like fun to program to me. Played around with them for a while, lost interest, moved on to other things.

tigerwillow1 said:

...The I/O bus was a daisy-chain with 6 cables in and out of each peripheral. I happened by shortly after he started the job, while he was carefully labeling each cable and recording where it went from and to. I volunteered to help and just pulled out all of the I/O cables and made a heap of them on the floor. Probably about 30 of them. I'll never forget the look of horror on his face while I was doing this. He didn't know that all of the cables are identical except for length, and once you know how the I/O bus works, it's easy to put it back together.

Click to expand...

Are you talking about IEEE-488/HP-IB cables? Dealt with them on stringing scopes, analyzers, etc. and later HP-UX workstations to tape drives, hard drives, etc.

My first home OS was CP/M, running on a home-built z80 system with two 5.25 floppy drives.

concord said:

Are you talking about IEEE-488/HP-IB cables?

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No, these were DEC-specific cables. I found a picture on the Internet of the newer flat cables. The ones we had were fat round cables, with the same circuit boards on each end. Some of the prices I paid in the past for computer parts look so outrageous today. For my first home-built system I bought two 5.25 floppy drives for $300 each (in the 70s). They were from Siemens because the mainstream brand I don't remember cost even more. I was using an Intel in-house development OS because I was using an Intel CPU board. The Intel OS was somewhat similar to MS-DOS but IMO better. In hindsight, Intel should have marketed that to IBM for the PC, but it was just an in-house development too with no thought of selling it. Intel also had a programming language called PL/M that was for in-house development and their single-board computer products. It's C-like but much less cryptic, and is my all-time favorite high-level language. I think it's long dead at this point.

^^^^^^^^
Look like they could be very fashionable belts!!!

concord said:

Are you talking about IEEE-488/HP-IB cables? Dealt with them on stringing scopes, analyzers, etc. and later HP-UX workstations to tape drives, hard drives, etc.

My first home OS was CP/M, running on a home-built z80 system with two 5.25 floppy drives.

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LoL, had to be careful who I was around back then when referring to IEEE- 488 standard. I made the mistake of calling it the HP-IB bus once in a corporate setting. Apparently some of the people took offense of the term HP-IB because that was a HP trademark. I was instructed to use the "correct, generic" term IEEE 488...
Ran into HB-IB bus stuff pretty often, mostly on HP plotters and lab equipment back then. We had stacks of HP-IB and other special cables... all ended up going to scrap metal processor.

One of my first "home computers" (PC type, didn't roll in on 19" racks) was a system made by Rair (sp?) Computing, ran a multi-user version of CP/M called MP/M. It too was Z80 based, had twin 5.25" floppies and a Seagate 10MB MFM harddrive (or 2). Had a mux board supporting up to 8 RS232 terminals. Interesting machine, but ended up as dust collector like most of my hardware.

I fell into computers when Columbia Data Products went tits-up. One of my investors in
my tire, front-end and brake business in Mission Viejo Ca. was paid off in finished computers.
They were stacked up in one of my extra rooms. I started selling them like hotcakes
to my automotive customers. In the 1st week I sold 25 "boxes"! He gave me 1 and that was
the beginning of a new profession.