
Building the System/360 Mainframe Nearly Destroyed IBM - headalgorithm
https://spectrum.ieee.org/tech-history/silicon-revolution/building-the-system360-mainframe-nearly-destroyed-ibm
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IndrekR
_The Mythical Man Month_ is a great collection of essays by Fred Brooks,
written about his experience in development of the OS/360 for this iron. Parts
of it are still very relevant for the engineers today.

* [https://en.wikipedia.org/wiki/The_Mythical_Man-Month](https://en.wikipedia.org/wiki/The_Mythical_Man-Month)

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maerF0x0
In your opinion what parts?

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segmondy
Well, to tell you how useful the book is. I own 3 copies and keep them by my
desk. When people ask why I tell them so I can read it 3x faster.

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gumby
Check out the photo of the obviously hand-made core memory -- the caption
implies it was a production unit. I am not sure if that is correct but the
photo above shows how manual the overall assembly was. It's true that back
then people were still bonding wires to transistors by hand in Mountain View
and Palo Alto, but that approach was already on its way out.

From those photos I can see how only 20 years before IBM had been able to
retool its factories to make machine guns for WWII. Nowadays such a radical
retooling seem inconceivable to me.

~~~
vmh1928
Remember that IBM had a long history building time clocks, card punch / sorter
equipment and cash registers. All mechanical devices. Going from that to a
device with a few moving parts that shot bullets was not a huge leap.

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slfnflctd
Utterly riveting for me, so many lessons to unpack here. No summary can do it
justice-- if you are at all interested in the history behind the importance of
portable software, read the whole thing. I did not realize the extent to which
IBM essentially 'bet the farm' on this concept.

Fun fact I just learned: some of the software written for these machines can
now run alongside Node.js on the same hardware. That's some impressive legacy
support.

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abraae
It's also an interesting twist on the Innovator's Dilemma. The lesson IBM CEO
Tom Watson took from the project was:

> Years later, when asked whether IBM would ever engage in such a massive
> project again, one executive barked out, “Hell no, never again.” Watson
> tilted toward a similar reaction. Commenting in 1966, he said, “At our size,
> we can’t go 100 percent with anything new again,” meaning anything that big.
> After the 360, Watson made it a policy “never to announce a new technology
> which will require us to devote more than 25 percent of our production to
> that technology.”

Yet if IBM had had the balls to hold onto that "bet the farm" spirit, then
they might not be quite the sad husk of a formerly great company they are
today.

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xref
Or they might have gone bankrupt decades ago :) the problem with betting-the-
farm is you’ve gotta win every time, one miss and you’re kaput

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vmh1928
Yes. There's a bit of survivor bias in this story and a tendency to look back
and think the outcome was inevitable. Although, if you look at the story of
the PC Division, there are similarities even though the scale and risk are
different. Both the S360 and PC were new creations built by empowered teams
that addressed issues with existing technology. Standard interfaces and
extensibility were a big part of the success of both stories. Not "open" in
the sense we use the word today but standardized - the ISA bus allowed the
extensibility of the PC via any number of peripherals, just as whatever the
cabling spec of the S360 was for disk, tape, card punch, sorting and
tabulating equipment. Enabled by software. A lot is made of the hardware story
here, it would be interesting to have part of the operating system development
story.

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xref
I think it was mentioned in an earlier comment the book The Mythical Man Month
is about the development of OS/360\. I’ve never read it but it may be more
“businessy” than what it sounds like you’re interested in

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lucas_membrane
Article mentions that 1401 emulation on the lower models of the 360 (models 30
and 40, I think), was a key to success of the 360's. I know that emulation
also ran later on larger and later models, 370's, etc. Anybody know when this
stopped? I recall one company still running 1401 autocoder (on an IBM 3090 or
something like it) until Y2k conversion was not feasible. Did any of those old
autocoder systems survive past Y2k?

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GeorgeTirebiter
That original emulation was actually in microcode; and it wasn't quite 100%
compatible with all the options and extensions that were possible for the 1401
(example: multiply and divide hardware was optional on the 1401).

Seems to me that pure software emulators (like the one written in BAL,
mentioned below) would not be subject to any particular kind of Y2K problem.

I think it was more of a problem of having very old 'working' legacy code that
nobody wanted to touch anymore. If one had the expertise, one could in
principle do Y2K fixes to (original) 1401 autocoder code.

There is excellent work by Ken Shirriff e.g.
[http://www.righto.com/2019/01/accounting-machines-
ibm-1403-a...](http://www.righto.com/2019/01/accounting-machines-ibm-1403-and-
why.html) that has much 1401 detail.

~~~
lucas_membrane
>> If one had the expertise, one could in principle do Y2K fixes to (original)
1401 autocoder code <<

By 1999 there were so many generations of 360 programs that read and wrote the
same files as the 1401 code that any changes to record formats (e.g. 4-digit
years) would have been very impractical. The worse date rollover for the 1401
code came in April of 1983, when months since 1900 reached 1000. Stuff like
that mostly got fixed with overpunches, but some of the record layouts were
running out of places to overpunch.

I read that page by Ken Shirriff when it was posted somewhere a few weeks ago.
Very informative.

> multiply and divide hardware was optional on the 1401 Weren't both floating
> point (wobbly precision) and packed fixed decimal each extra-cost options on
> the first 360's?

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dmckeon
> In the first month following the S/360 announcement, customers worldwide
> ordered over 100,000 systems.

Orders equal to 5 times the installed base in US, US, EU, and JP, at a
development cost of $50k/order [5 billion $/100k orders = 50k in 1965 USD,
~400k in 2019 USD].

From a software perspective, Brooks’ book was educational, but from a business
perspective, the order numbers are inspiring.

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lucas_membrane
> over 100,000 systems

Where did that number come from? How many were model 20's? That would be 100
mainframes for each company in the Fortune 1000. How many of the 100,000 were
installed and paid for? At even a low $50k per machine, that would be almost
double IBM's total annual revenue in the mid 1960's, and they sold lots of
punch cards, tabulators, sorters, collators, printers, minicomputers (1130's
machines would have taken and 1620's, right?), calculating card punches, disk
drives, tape drives, data cells, YNI. I toured the IBM mainframe production
line at Poughkeepsie in early 1967, and it did not move quickly nor was it a
beehive of activity, maybe 5 machines in process, and none of them moved in
the 30-60 minutes I was there. I did not get the idea they could churn those
things out in the 1000's.

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patrickg_zill
They had $750 million worth in inventory before they were able to build and
ship their first system.

Afterwards they were hiring something like 1000 new people per month...

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bogomipz
>"In mid-1963, engineers in the Poughkeepsie and Endicott laboratories had
begun exploring the possibility of adding special microcode to the control
stores of computers to improve their performance when simulating earlier IBM
computers.”

Does anyone know did IBM invent microcoded control stores then? This is pretty
fascinating.

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fanf2
Microcode was invented as part of the EDSAC 2 project at Cambridge University
in about 1957. EDSAC 2 was also the first bit-sliced hardware design (which
made it easier to replace parts that had failed).

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bogomipz
Interesting thanks. What is "bit-sliced hardware design"? I am not familiar
with this term.

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ThrowawayR2
Always fascinating to read the history behind the giants of early computing
history. We tend to forget that IBM was one of the FAANGs of its era, creating
systems and technologies that transformed the world before relative newcomers
like x86 or UNIX even existed.

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rmckayfleming
THE FAANG of its era.

~~~
jhallenworld
To give an idea, read this 1974 article:

[https://reason.com/archives/1974/04/01/ibm/print](https://reason.com/archives/1974/04/01/ibm/print)

"the 1956 consent decree (which settled the 1952 suit) placed significant
restrictions on IBM's computer business [4], and is responsible for the very
existence of some segments of the computer industry. It required that IBM sell
its machines as well as lease them—there are now over a hundred firms whose
sole business is leasing IBM computers! They buy from IBM, depreciate the
machines over a longer lifetime, and charge lower rental fees.[5] (Recently
some of these leasing companies have expressed their desire that IBM be forced
out of the leasing business altogether.[6])

Another provision of the decree aided the growth of the computer services
business. It required that IBM operate its services business as an independent
(wholly owned) subsidiary, Service Bureau Corporation (SBC), and that any
equipment and services provided for SBC be on the same terms as for any other
company. Ironically, as part of the settlement of the CDC suit last year, CDC
bought Service Bureau Corporation from IBM, and since CDC is not under any
antitrust restrictions, it expects SBC to be much more profitable! [7]

The 1956 decree also required IBM to train personnel and provide technical
manuals for anyone who owns, repairs, maintains, or distributes IBM electronic
data processing equipment. The decree also ordered IBM to grant unrestricted
licenses to companies desiring to use its patents, and enjoined IBM from
instituting any suits for patent infringement which occurred prior to the date
of the decree.

The aim of these provisions was to cut IBM's share of the market and to
"enhance" competition."

At the time, the computer industry was known ato be made up of "snow white and
the seven dwarfs": "Snow White was IBM and the seven dwarfs were Burroughs,
UNIVAC, NCR, Control Data Corporation, Honeywell, General Electric and RCA"

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GeorgeTirebiter
I also heard it as "IBM and the BUNCH" (Burroughs, Univac, NCR, Control Data,
Honeywell)

'in the day' I don't ever remember seeing a GE or RCA box, but the others
seemed to thrive in their niches.

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gumby
simultaneously launching all those processors and peripherals is the opposite
of today's doctrine of "start with a minimum viable product and expand from
there"

