Discussion

Ken Shirriff's blog

kens: Author here: I've finally finished a detailed history of IBM's 4 Pi computers, powering everything from the B-1 bomber to the Space Shuttle. Let me know if you have questions...

nick__m: just one: why it named System/4 Pi ? (the Pi part especially)

rootusrootus: Back when I was in the USAF they told us 4 Pi was because it was essentially two IBM 360 mainframes in parallel. Probably BS but that was what we all thought.Really happy to see this history lesson in any case, I had mostly forgotten about my experiences from the mid 90s.

kens: You're right, that's BS :-) Yes, many of the 4 Pi systems were essentially IBM 360 mainframes; some were completely compatible, while others were more "inspired" by the 360. However, only the little-used EP/MP model was a multiprocessor system. As for the name, IBM made it clear that the name comes from 4 pi steradians in a sphere.What 4 Pi systems did you work with, by the way? Do you have any interesting stories?

rootusrootus: Nothing too interesting I’m afraid. The unit I was in was responsible for the 4 pi software on the E-3 AWACS. If memory serves, this was right about the time of block 30/35 rollout. I looked recently and they’re running much newer, better computers these days (it’s been 30 years, now I feel old).We used to say that the computers were so heavy that the E-3 was routinely taking off over its maximum takeoff weight :). Another likely bit of BS. But it did take that old bird well over a minute of takeoff roll to get airborne, which is weird when you are used to airliners. I did not regularly get to ride in one, we mostly used a 4 pi in our E-3 simulator. Did a lot of “external testing” which was mostly very tedious but we did get to talk to interesting people.