A very interesting article about an interesting, late (in more senses than one) and little remembered computer: https://www.theregister.co.uk/2013/06/28/30_years_on_the_story_of_the_memotech_mtx/?page=3

says this:

Coming as the MTX did from the SM1, it was decided very early on that it would measure up to the de facto standard width of a business computer, 475mm, and that it would be clad in Memotech’s trademark black anodised aluminium. The extra numeric keypad and function keys were added because the Qwerty deck alone looked lost among the acres of metal.

I never heard of a de facto standard width of a business computer before. Where did that come from?

  • Strictly speaking, the MTX didn’t connect to the FDX “via RS232”. It connected through an expansion card that had the bus interface chips and also RS232 chips (which were usually populated).
    – Andy Key
    Mar 17, 2019 at 17:24

1 Answer 1


I never heard of a de facto standard width of a business computer before.

No there wasn't one. Beside the fact that defacto is quite vague if not said in conjunction with a specific example, there was no generally adopted. Especially not in 1983, when everyone was still making different machines with much differing features. The fact alone that Memotech did design their own layout does show that there wasn't a conform standard to follow.

Where did that come from?

Most likely it's an euphemism to avoid saying 'IBM', as the PC/AT Keyboard did measure 47.5 cm (PC/XT was 45.5).

Many nice (read more than just the typewriter field) computer keyboards ranged between 40 and 55cm. Thus computer furniture is made to accomplish these sizes. Building a keyboard at or slightly below 50 cm is therefore a good idea, so why not just take it from the emerging machine made by this three letter company.

  • 7
    Of course, it's worth noting that 475mm fits conveniently in an industry-standard 19" equipment rack (which has a 482mm opening size), which could be what's being referred to?
    – Jules
    Aug 19, 2018 at 13:42
  • @Jules 19" wasn't as much a thing in 1983 than it is today. And it still is anything but a 'business' computer - aka desktop/office machien.
    – Raffzahn
    Aug 19, 2018 at 13:51
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    @Raffzahn mini-computers were rack-sized well before the 80s (as I suspect you know well), and 19” racks have been standard in other contexts since the 20s. Even if they weren’t a direct factor in office computer design, they could have had an indirect influence (e.g. on acceptable motherboard sizes). Aug 19, 2018 at 13:58
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    @Raffzahn perhaps I misunderstood, I read “I never heard of a de facto standard width of a business computer before. Where did that come from?” as referring to computers, not keyboards. The quoted article is about a keyboard, but it compares its size to a “de facto standard” for computers, not keyboards. Aug 19, 2018 at 15:32
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    @tofro It's a keyboard computer, as everything is in the keyboard. FDX/HDX is an optional unit, connected via RS232 (!) to the computer. Neither AT form factor, not anywhere a part of the computer. The only floppy expansion direct connected was the SDX, which plugged into the expansion port on the left side, making the machine look a bit like a CPC.
    – Raffzahn
    Aug 20, 2018 at 14:10

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