The 360 - IBM's $5 billion gamble

IBM’s $5 billion gamble - the System/360. A whole family of machines. Here’s a particularly impressive console, of a 360/91 in NASA’s Goddard Space Flight Center:

(From wikimedia)

Some nice anecdotes here about working with a model 67:

This is the front panel and operator console of one of the CPUs. As you can see, IBM went nuts on incandescent lights for the various machine registers, but the only one that really mattered was the WAIT light, which lit when the machine wasn’t doing anything.
At that time every IBM mainframe came with a resident hardware engineer who fixed things on the spot, should something break. Before transistors, mostly what he did was replace 12AT7 vacuum tubes. Later as seen here, there wasn’t a lot to do except watch the log.

More about IBM’s big bet:

IBM’s revenue in 1962 was $2.5 billion. Developing System/360 cost twice that. Company president Tom Watson, Jr. had literally bet the company on it. Watson unveiled System/360 in 1964 — six computers with a performance range of 50 to 1, and 44 new peripherals — with great fanfare. Orders flooded in. The gamble paid off.

production and sales of the System/360 meant a complete re-engineering of the company’s development resources, processes and strategy. In addition to posing a daunting marketing challenge, it would also kill off IBM’s golden goose—a disorganized but very profitable line of existing computer products.
Within eight weeks of the announcement, clients had ordered well over two thousand machines.

Michigan Terminal System


Content above from an earlier post to Retro Computing on G+, where Neale Ferguson noted:

The 67 gave us virtual machines with CP-67 a follow on to CP-40. This eventually became VM/370, VM/SP, VM/ESA, and today’s z/VM. Special circuitry was added to the 67 to give it virtual memory via direct address translation (DAT), which wasn’t part of the original 360 architecture (the project was already risky enough). I’ve posted this before but it’s worth repeating: Also, you can still get the MTS executables, just Google it.

The idea for this a blog post by the HNF here:
The Computer of the Century [in German] but rather shortly after, and surely by coincidence, we see an article from the IEEE:
Building the System/360 Mainframe Nearly Destroyed IBM
with this excellent photo of the production line:

(Photo by IBM)

From that second article:

In the years leading up to its 7 April 1964 launch, the 360 was one of the scariest dramas in American business. It took a nearly fanatical commitment at all levels of IBM to bring forth this remarkable collection of machines and software. While the technological innovations that went into the S/360 were important, how they were created and deployed bordered on disaster. The company experienced what science policy expert Keith Pavitt called “tribal warfare”: people clashing and collaborating in a rapidly growing company with unstable, and in some instances unknown, technologies, as uncertainty and ambiguity dogged all the protagonists.


A nice set of console pictures:

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Very nice, thanks! I see what’s happened: we’ve hit the 55 year anniversary. There’s a 1964 promo video in the HNF blog. Here it is:

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Vintage 1966 film excerpt from the IRS showing how an IBM System/360 mainframe system is used in their tax processing data center. About 4 mins long, color and narration. Nice view of a 1960’s era data center and the System/360 master console. This excerpt focuses on the System/360. The full version of this film is called “Right on the Button” and is also available on YouTube. The model numbers of the equipment seem to have been taped over by the IRS film maker, but it is clearly the IBM 360, and its tape, disk and punch card peripherals. Fun to watch…

1966 -1967 IBM System/360, IRS Data Center


Thanks @guille! Using Ken Shirriff’s handy console identification guide, as posted upthread by @wazoox, I think we can say this central system was a model 65 or 67?

Edit: an interesting cassette kind of storage just after the 1 minute mark in the video. I haven’t seen that before. I bet @MaggieL can identify it!

Edit: Oh, here we are, the 7340 hypertape drive

A new Model 3 of the 7340 was developed to provide a double-density option of 3022 bytes per inch, in addition to the 1511 bytes per inch of the Models 1 and 2, thereby doubling the data rate to 340,000 bytes per second. The Model 3 was announced in April 1964, and the first customer shipment went to the U.S. Internal Revenue Service in West Virginia in mid-1965.

Probably related to the S/360 anniversary, LGR has added a nice video on the IRS system and its 2018 outage related to its legacy software. Somewhat of a fable on IT and integration in general.

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Ah… I wish I have more time available to comment/post/discuss… Yes, 1965, that’s what look to me.

Ken Shirriff has put up a very informative post on the 360’s core memory:


I saw a cool photo of the production “line” from system 360s, and every one that was being built, had a sign over it that had the name of the customer, which I thought was a nice detail.

I see you mentioned Ken Schiriff. He routinely appears on CuriousMarc’s videos restoring all sorts of cool old tech. Curious Marc owns a ton (literally) of 360 hardware and I think plans to restore it, and get some sort of system working.

I also found these guys in the UK who found a 360 in Germany and are relocating it to the UK for a restoration: