[HN Gopher] The rise and fall of IBM's 4 Pi aerospace computers:...
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The rise and fall of IBM's 4 Pi aerospace computers: an illustrated
history
Author : zdw
Score : 60 points
Date : 2026-03-29 16:26 UTC (6 hours ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| kens wrote:
| 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 wrote:
| just one: why it named System/4 Pi ? (the Pi part especially)
| kens wrote:
| 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: 4p 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."
| jasomill wrote:
| My local carwash's top-end wash is called the "Ultimate
| 360deg", despite the fact that it obviously cleans the
| entire surface area of the car, and I'm simultaneously
| annoyed by the name and reminded of the System/4 Pi.
| moffkalast wrote:
| And a follow up, was the Raspberry Pi named as a joke
| reference to these?
| chihuahua wrote:
| Could a single person lift the complete set of manuals for one
| computer model?
|
| And what percentage of the pages of the manual said "this page
| intentionally left blank"?
| contingencies wrote:
| Are there any similar parallel series in China, France,
| Germany, India, Japan, Russia or the UK that you have had a
| chance to study?
| kens wrote:
| I'd like to study aerospace systems from other countries.
| Unfortunately, it's even harder to get information on foreign
| systems than US systems.
| decryption wrote:
| You mentioned in the post that you "received a stack of 4 Pi
| marketing brochures and articles". Do you plan to scan these
| and place them on your website or the Internet Archive? I'd
| love to read them!
| rootusrootus wrote:
| 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 wrote:
| 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 wrote:
| 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.
| kens wrote:
| The E-3's computer was definitely heavy: the brochure that
| I have says that it weighed 1,826 pounds. (There's a nice
| photo of the refrigerator-sized cabinet full of circuit
| boards in my article.) The 4 Pi line is kind of strange; it
| has all these compact 60-pound computers, and then they
| throw in a couple of monster systems that weigh almost a
| ton.
| kens wrote:
| Actually I'm mistaken; the AWACS CC-2E computer was also a
| redundant dual processor system.
| jeffs4271 wrote:
| Cool stuff. Worked next to these one summer at IBM on dev tools
| that ran on PC. But never knew much about them. They were in the
| thick aluminum case and you didn't touch them!
| neilv wrote:
| This triggered a tangential memory of encountering this kind of
| aerospace computer box.
|
| I was a teenage intern at a very serious software engineering
| company, which was doing bespoke high-end in-circuit emulators,
| integrated into a full-lifecycle software engineering platform.
|
| One time I wandered into the hardware engineering area, there was
| a customer box looking a bit like the later-model photos in the
| article, just sitting on an EE bench. (Though my vague memory is
| that it might've been something like Honeywell or Rockwell?)
|
| As a teen, with so may things to learn about workstation networks
| and software engineering, and working professionally for the
| first time, and becoming an adult... It was awhile before I
| slowly learned who were the customers for all this platform the
| company developed. It was for people who make complex, critical
| systems -- mainly military, aerospace, and datacommunications. So
| it was just further overwhelming wonder: people use our stuff for
| aircraft and spacecraft?! So cool!
|
| Later in my career, I have more context, to decide the kinds of
| things I want to work on. I'm also often involved when we _start_
| with the understanding of the customer, and the building cool
| stuff tends to follow that. Some of the AI toys recently elicit
| some of that earlier wow of everything being new and cool, but
| now knowing more context, and seeing through some of the current
| marketing noise.
| e-topy wrote:
| I don't know how to put it into words, but this aesthetic of
| computers just looks sooo good. Makes me want to try making my
| homelab/experimental hardware look like it. Any ideas how to
| source parts that look similar in low quantities?
| newsclues wrote:
| military surplus
| kens wrote:
| It's easy to get the military round connectors from Digikey; it
| just isn't cheap :-) eBay is your best bet for an affordable
| price on them.
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