IBM's Alternate Future: Solid Logic Technology

I wonder if all the parasitic capacitance from the shielding and ground planes was enough to function as decoupling. I also wonder if anyone's ever implemented one of these IBM system 360's in a single FPGA!

Circuitmike

Wow, memory lane episode Fran. I too took a FORTRAN class using punch cards made on a machine with a keyboard that jumped and bounced. When I worked at HP we used to repair some boards by drilling down to inner layers and soldering a jumper wire to fix an open trace. Did you see how shiny the solder was on the back of the 7400 series board made in the 80's 30+ years later?

Fascainting.. I still remember being utterly amazed by IBM microdrives.. They really were innovative in a way other companies don't seem to be

veritanuda

Fran, I started programming S/360 computers in college and got my first professional programming job upon graduating in 1970. I was a systems programmer at Rutgers University and, when I started, we had an S/360 Model 67 running OS/360 MVT which, to me, was the ultimate machine analog because, naturally, it could do anything. If it hadn't been for my falling into that field, I probably would have been a machinist. A lot of the PR hype at the time involved so-called computer generations, 1G using vacuum tube logic, 2G using discrete transistor logic, and 3G, using integrated circuits. As you know, IBM circuit boards of the time were unique and, actually, beautiful. A lot of them viewed in profile looked like skylines, with the SLT cans the warehouse district. And we we're in awe of SLT, never mind the fact that my wrist watch is a good deal more powerful than that 360/67, and the fact that our system was powerful enough that we could support several hundred interactive users (We ran Call/OS for student conventional programming, APL for, well, you know, APL, and ATS for interactive word processing). What prompted this comment was your discussion of the four layer boards you had, and I have a vague recollection that by the end of the '70s, at least, they had seven layer boards, and in the latter days, I think they even extended it to 12 layers, the pages and smaller chip boards still looking about the same as the examples you have. Jeff

Jeffrey R. Broido

The S/360 instruction set was so rich that AL was almost a higher level language. I was forced to retire from the systems programming field in 2000, and I so missed assembly programming that I installed an S/390 emulator on my PC, including installing a purloined copy of OS/390. I even had some people in India whom I was tutoring, logging in to do their homework. I maintained this for 4 years until I finally was able to taper off! STM R14,R12,12(R13). Keep your save area dry!

Jeffrey R. Broido

IBM did make some amazingly good systems. The entire System 360 series was genius. Assembler code written for a 360/30 would run just fine on a 360/65. I learned programming OJT starting in 1969 using assembler on a 360/30 with 32K of memory running DOS/360 - and no degree.

Michael A Klaene

Fantastic deep dive. Love it!

Fred Niell

Considering IBM's monopoly on computing through the 60s and 70s, I think it's fair to say these SLT packages were the next big thing in that field. Too bad IBM wasn't into publishing any literature on these things or other companies might have been able to adopt them as a universal standard.

Great Joe

I used to work on 360/370 systems. What a bit of nostalgia! Glad we have moved on to better things.

William Alsing

Amazing! I have not seen one of those boards since the early 80s. There was an IBM service center very close to my house and they had not one, but TWO standard dumpsters. All during the 70s I'd raid their trash and find those boards every week. The only nasty thing in their trash were coffee grounds and ash tray contents. But neither deterred me from digging parts out. As a kid, I too opened the caps of those square devices to see what was inside. I distinctly remember that once the cap was off there was a clear layer of clear gel on top of the circuitry. Maybe it dried out on your sample? Try running your finger over the top of the ceramic square and see if there is anything sticky still left on top of the components. They also had larger sizes of those packages that housed more parts, but were the same as your small sample, just more of it. The really great thing about the IBM parts were that they were always clean. Never any dust on any of it, except some power supplies that used fans. I didn't know about the TTL family yet and there was no way to find documentation about IBM components. In the early 80s someone gave me a book by Texas Instruments called "The TTL Cookbook". But all of those awesome IBM circuit boards turned out to be useless because they house-marked all of the chips and transistors. There was no way to cross-reference the custom IBM part numbers to an industry standard TTL or CMOS device. They had this amazing version of magnetic core memory that would take too long to describe. Seeing your boards was a fantastic jump back to my childhood. Thank God there was no such thing as recycling back then and you could throw whatever you wanted into the trash. They also threw out reels of 1/2" computer tape, punch cards and microfiche made only for their own display units. Collins Avionics also had its own Printed Circuits Division and they made multi-layered boards very much like the IBM version. The traces all went horizontally on one layer and then vertical on the flip side of the board. Then they just got better about multiple layers and the final board layout used every bit of board space for parts since avionics required the maximum amount components in the smallest space possible. Collins made the radios for the Apollo program and they have a little museum where employees can see the radio tune head and associated boxes used on the missions. Neil Armstrong's first steps on the moon were transmitted on Collins radios. RCA made the camera, but Collins transmitted and received the signals. It was obvious from looking at those parts from the 60s that they did an incredible job of packaging and wire protection. Collins even developed a mainframe computer to compete with IBM and Control Data, but only were able to sell a few computers as it was impossible to displace IBM even if your product was better in some way. So these IBM boards of yours, as you said, were on 60s-era mainframes that I know kept servicing will into the 80s. You can learn a lot from a company's trash. It was just so cool to see someone opening one of those mysterious square packages like I did so many times as a kid. Thanks for the GREAT memories!

Matt Wietlispach