Ancestors

Written by Ken Shirriff on 2025-02-01 at 18:56

What is the origin of the word "mainframe"? Digging through archives, I traced it back to 1953. The IBM 701 computer was built from "frames": power frames, a storage frame, a drum frame, and the main frame. This 1953 drawing from the Installation Manual shows the dimensions of the "main frame". 1/n

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Toot

Written by Ken Shirriff on 2025-02-01 at 18:56

IBM's construction of computers from frames was a major innovation: the frames fit through doors and were transportable. Earlier computers were often constructed in place and difficult to move. Photo shows an IBM 701 at GE with frames for power and drum storage, and main frame in the center.

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Descendants

Written by Ken Shirriff on 2025-02-01 at 18:58

IBM's engineering documentation extensively used the term "main frame". The documentation described the location of each tube in the system. The abbreviation "MF" indicated the tube was in the main frame, as in the schematic diagram. 3/n

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Written by Ken Shirriff on 2025-02-01 at 18:59

From the 1950s to the 1980s, the word "mainframe" indicated the physical box or cabinet that held the computer. Even a personal computer had a "mainframe". 4/n

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Written by Ken Shirriff on 2025-02-01 at 18:59

At the same time, "mainframe" took on a different but related meaning: a computer's CPU (central processing unit). By the 1980s, however, this definition faded away: a book stated: "According to the official definition, 'mainframe' and 'CPU' are synonyms. Nobody uses the word mainframe that way."

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Written by Ken Shirriff on 2025-02-01 at 19:00

With the development of the minicomputer and the microcomputer in the 1970s, "mainframe" moved towards its modern meaning, with computers partitioned into micros, minis, and mainframes. IBM started using "mainframe" as a marketing term in the mid-1980s; e.g. calling the S/390 "mainframe class". 6/n

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Written by Ken Shirriff on 2025-02-01 at 19:00

Analyzing newspapers shows the rise and fall of the term "mainframe". The term became popular during the 1980s. At the end of the 1990s, as the popularity of mainframe computers dropped, usage of the term steeply dropped too. 7/n

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Written by Ken Shirriff on 2025-02-01 at 19:01

For more on the history of the word "mainframe", see my latest article: https://www.righto.com/2025/02/origin-of-mainframe-term.html

Thanks to the Computer History Museum for letting me examine their archives.

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Written by Ken Shirriff on 2025-02-02 at 18:56

Colossus didn't use the term "frames". It was built on 90-inch racks, called the J rack, K rack, S rack, C rack, and so forth; see https://www.codesandciphers.org.uk/lorenz/colossus.htm

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Written by Mark Crocker on 2025-02-01 at 19:42

@kenshirriff they also use the word screen very differently than the modern context 🤣

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Written by lopta on 2025-02-02 at 02:44

@mcrocker @kenshirriff Remember when a monitor was a certain small software utility?

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Written by Vertigo #$FF on 2025-02-01 at 19:46

@kenshirriff Tagging #mainframe (see up-thread)

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Written by ezra on 2025-02-01 at 20:34

@kenshirriff have you and david talked about editing some of your posts into a book? MIT press should gobble this up

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Written by root42 on 2025-02-01 at 20:39

@kenshirriff wasn‘t CPU also sometimes not just a chip but maybe a whole PCB or even chassis?

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Written by Ken Shirriff on 2025-02-01 at 21:25

@root42 Yes, the "central processing unit" was defined as "A unit of a computer that includes the circuits controlling the interpretation and execution of instructions. Synonymous with main frame". Sometimes storage was considered part of the central processing unit.

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Written by Stephen Illingworth on 2025-02-01 at 21:28

@kenshirriff @root42 I've heard people referring to the case of a PC as the "CPU". I didn't like it.

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Written by Matthew Miller on 2025-02-02 at 00:08

@JetSetIlly @kenshirriff @root42

Yes, me too. Like, as opposed to the monitor or keyboard or other peripherals. This history shows these people were more attuned with the origin of the term than we were!

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Written by 💞 eva 💞 on 2025-02-02 at 14:34

@mattdm oh dear, making me feel old this early on a Sunday! I remember all of those terms, from spending my after-school hours at the US Naval Academy's computing rooms. Some of my best childhood memories.

This thread is great! Thanks Ken!

@JetSetIlly @kenshirriff @root42

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Written by Henrik Kramselund - kramse 🍉 on 2025-02-03 at 08:34

@JetSetIlly @kenshirriff @root42 they also have used "the hard drive" for the whole PC, equally annoying

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Written by Ben Galehouse on 2025-02-02 at 10:51

@root42 @kenshirriff My father had a PDP-11/45 in our basement when I was a kid. The CPU was a stack of perhaps 5 boards of discrete TTL chips (a few flip-flops or what-not per chip) and a lot of wirewrapping on the other side of the backplane to connect them. Next to that was the FPU, which was larger - maybe 12 boards if I remember right.

Keeping it working often meant identifying the chip which went bad. To assist with this, he managed to acquire an extender to hold a board out from the backplane a bit, which gave more room (though still not a lot of room) to clip on leads to connect to the oscilloscope/logic analyzer. However, using them required downclocking the CPU, which occasionally made the fault go away.

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Written by Thomas Amberg on 2025-02-01 at 20:47

@kenshirriff reminds me of https://www.flickr.com/photos/tamberg/54277912940 (Hohner-CPU, 50ies)

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Written by Sander Antoniades on 2025-02-01 at 19:10

@kenshirriff I'd be curious of the usage in popular culture. Movies continued to use mainframe as a term for big computer much in the same way they use firewall as only defense against hackers.

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Written by Ken Shirriff on 2025-02-01 at 19:35

@s4ra8s I don't know about pop-culture usage, but I have a graph of popularity of "mainframe" in Google Books. Mainframe peaks later than minicomputer and microcomputer, most popular in the late 1980s.

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Written by author_is_ShrikeTron🔠💉x7 on 2025-02-01 at 19:41

@kenshirriff Tidbit, it still exists as a job-category/function in California's unemployment system.

Yes that system is very out of date.

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Written by Jake Hamby on 2025-02-01 at 20:29

@ShrikeTron @kenshirriff I think California's unemployment system is running on a mainframe. The state government is now renting time on their mainframes to counties so they can get rid of their mainframes.

https://statescoop.com/los-angeles-moves-mainframe-california-data-center/

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Written by Kat on 2025-02-01 at 20:04

@kenshirriff Wait. So all this time, the movie pronunciationt that's caused me to grind my teeth so many times has in fact been canonically valid?

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Written by Riley S. Faelan on 2025-02-01 at 20:25

@kenshirriff What was MF3J29?

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Written by Ken Shirriff on 2025-02-01 at 21:28

@riley MF3 J29 probably indicates the tube module is in panel #3 in the main frame, row J column 29. I don't have the 701 doc handy, so don't quote me on the details :-)

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Written by Riley S. Faelan on 2025-02-01 at 21:30

@kenshirriff Did these tube modules have some sort of common AND / OR / NOT structure?

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Written by Riley S. Faelan on 2025-02-01 at 20:24

@kenshirriff #retrocomputing, though

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Written by Glen Turner on 2025-02-02 at 03:58

@kenshirriff not sure it was IBM's innovation. Flower's Colossus was built on UK Post Office phone system relay frames. The ability to move the computer also being the rationale, in this case from the Post Office Research Station to Bletchley Park.

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Written by Programmer 832-529 🍅 on 2025-02-02 at 04:16

@glent @kenshirriff

Yeah, frames are used in telephony and railway signalling. It basically means a chunk of electrical stuff on some sort of shelf or cabinet. Makes sense when IBM were trying to describe their setup they looked around at what else looked a bit like it and used that word.

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Written by ezra on 2025-02-02 at 20:06

@kenshirriff I did a very partial and brief history of rack formats in my chapter on modular synthesis in https://www.taylorfrancis.com/chapters/edit/10.4324/9781003219484-2/preface-patched-material-discursive-history-modularity-control-voltages-ezra-teboul?context=ubx&refId=53b96662-367a-4ba6-a0eb-21c2d8698677

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Written by Peter van Heusden (he/him) 🗿 on 2025-02-03 at 05:31

@kenshirriff in that second picture, where are the cables? That doesn't look like a raised floor (with some kind of logo in the middle?) and the "frames" are on little legs... I wonder where this fits in the history of datacentre design.

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