The IBM Model M Enhanced Keyboard is turning 40!

[Admiral Shark]

If you wasn't aware, around about now is pretty special for keyboards as this is the season that one of the most iconic keyboards is having its 40th birthday! The IBM Enhanced Keyboard (101/102-key Model M) is known for nailing the ANSI and ISO physical layouts sans super keys and the modern full-size keyboard, pretty much becoming an keyboard if you will, but also doing so in style with its (usually) buckling spring keyswitches. The story is spread across a few dates, but today in particular is 40 years since the IBM 3161 and 3163 ASCII Display Stations were announced! If you're not familiar with them, terminals with built-in IBM 3101 emulation but also capable of emulating various third-party terminals from ADDS, DEC, Hazeltine, Lear Siegler and TeleVideo (depending on 3161 or 3163 and installed cartridge.) These were the first IBM terminals to ship with an IBM Enhanced Keyboard.

Last month, on the 21st May, it was also the 40th anniversary of the IBM 7531 and 7532 Industrial Computers' announcements, the earliest recorded IBM Enhanced Keyboard host by announcement date. Whilst 753X was announced ahead of 316X, 316X beat 753X to market as they started shipping in July 1985 whilst 753X started shipping in Q4 1985. The 753X's Enhanced Keyboard was the first "industrial-grey" and PC-compatible variant, whilst the 316X's was the first pearl-white and terminal-compatible variant. Neither were the first Model Ms/membrane buckling spring keyboards in general (that honour falls to the IBM Wheelwriter 3 and 5 keyboards, whose 40th was last year), but these were the collectively the first Model Ms outside typewriters and became the default Model M. Eventually, the 753X Enhanced Keyboard will be modified to become PC/XT and PC/AT Enhanced Keyboards in April 1986 and most famously the PS/2 Enhanced Keyboard in April 1987.

On 21st May 2025, I wrote entirely on that afternoon an article as a sort of 'high-levelish' crash-course but also celebration on the IBM Enhanced Keyboard. If you fancy a read, please do: https://sharktastica.co.uk/articles/enhanced_40 (I was originally intending to post this here on that date, but things happened)


Courtesy of IBM Archives (link to full scan at the bottom) (also note Model M's original Keyboard G/Model G designation being used here)


IBM 7531/7532 Industrial Computer Keyboard (donated photo, CC BY-NC-SA 4.0)


IBM 3161 ASCII Display Station Keyboard (by P. Zwettler, "All Rites Reversed")

Here is some further reading if you fancy, as well:
* IBM 7531 announcement letter
* IBM 7532 announcement letter
* IBM 7531/7532 Technical Reference (chapter 4-1 for the keyboard)
* IBM 3161 & 3163 announcement letter
* Lexington Today - Tuesday, June 18, 1985
* My Model M Enhanced Keyboard wiki page

 

[itsemast]

This keyboard truly is a legend! If you buy a generic keyboard today, it's definitely based on Model M layout.

Looking at the photos of the PCB, I noticed that the microcontroller on the board is 6805, not MCS-48 like I always thought. Were any of the firmwares dumped and analyzed? It's likely to have Mask ROM, and dumping should be pretty hard. Well, i8042 firmware was dumped somehow, so this should also be possible.

One particular feature of Model M firmware that I am interested in is XT/AT autodetect. While other keyboards of that time had a switch to change mode between XT and AT, this keyboard could somehow guess, which system it was connected to. Anyone has any idea, how this was implemented?

 

[apl-vade-mecum]

Thanks for the photos! Back in the early 1980s, I heard that IBM's human factors research groups spent a lot of time on the arrow key layout. Typical early terminals might have four arrows like this:

^
< >
v

with a home key in the middle, or sometimes like the IBM 3277:

^ v
< >

Or as on the DEC VT100:

^ v < >

The IBM researchers came up with what they called the inverted T layout and testing showed that typists were faster & more accurate with the inverted T than existing layouts.

^
< v >

Well here we are today, I still really like the inverted T layout. Human factors folks did a nice job!

 

[traveler_aa5]

Some of the human factors guys were clowns. I was working on the 3890/XP check sorter conversion from OS/2 16-bit text mode to 32-bit GUI. The human factors guy INSISTED that I make an option for a screen without a command line, usable with a mouse. I insisted that was a bad idea. For the following reasons

1. No customer had requested it.
2. But mainly, because moving the mouse around while sorting would result in machine checks because the sorter interrupts weren't being serviced soon enough. (80 interrupts/sec).

I was overruled, and had to spend a week designing a Dialog without a command line that was never used.