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The rise and fall of IBM's 4 Pi aerospace computers: an illustrated history (righto.com)
rootusrootus 21 minutes ago [-]
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 13 minutes ago [-]
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?

kens 1 hours ago [-]
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 27 minutes ago [-]
just one: why it named System/4 Pi ? (the Pi part especially)
kens 25 minutes ago [-]
The name is essentiallly a geometry joke. The IBM System/360 line of mainframes (1964) revolutionized the computer industry with the concept of one family of computers for all applications: business and scientific. (Before the 360, nobody considered compatibility, so different computer models were entirely incompatible, which was a mess.) The name symbolized that System/360 covered the full 360º of applications.

The 4 Pi name extended this idea to applications in the 3-dimensional world: 4π is the number of steradians making up a full sphere. As IBM put it, "System/4 Pi also fills a sphere—the full spectrum of military computer needs—for airborne, space, or shipboard use."

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