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Comment by jimmaswell | Hacker News Reader

I've become familiar with it playing with the Kaypro 1 (the last CP/M model, not the first Kaypro - their model numbers are confusing). I picked it up years ago and just got around to getting disks etc recently.

Interesting to see the influence on DOS, and how people used to deal with ED to write assembly etc.

Really nice machine to play Zork and such on. The monochrome green is so clear and nice, and a really good size. Keyboard feels great.

I've been trying to get serial working with the odd pinout without success yet.

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I got to use CP/M briefly on a DEC Rainbow machine in the 80's. It was very similar to DOS but IIRC there were quite a few differences at the detail level. I remember seeing some ads for Kaypro's but I don't think I ever saw one in real life... What sort of issues are you having with the serial port? You might need to jumper the flow control pins if you can't disable flow control. I'm sure the pinout is documented? I had to deal with lots of oddball serial ports way back when, I might even have some breakout/jumper RS232 adapters lying around.

I finally figured it out today, I needed to use the modem port and a another different pinout. I'd been reading about the wrong kaypro before I think. I checked the pins with an oscilloscope and read the manual to figure it out. Pretty satisfying that it's working and it's also nice to finally close up this breakout connector and wire I got a while ago to make the "Kaypro cable".

I worked at a computer store in the mid 80s and we sold the heck out of Kaypros because they were a bargain next to DOS machines. They came bundled with software and often times a promotion with a bundled printer as well.

They tried transitioning to add DOS support with an addin card but it was too late to save them as PC and Apple became the defacto standards.

There was a little-known multiuser CP/M variant called MPM and we managed to sell a few of those, too. It was a cool if plain OS.

I have never heard of MPM. Thank you for the reference.

I ram MP/M 2 on an Altos and it was an excellent system. I think up to about half a dozen users sharing the system, surprisingly good performance for word processing tasks.

MP/M led to Concurrent CP/M-86, which in turn led to three separate families of OSes:

• Multiuser DOS (native 32-bit multiuser multitasking DOS-compatible).

• DR-DOS (DR's comeback, a better DOS than MS-DOS, available at retail, which spurred MS into creating MS-DOS 5, then 6, then Windows 95).

• DR FlexOS: realtime multitasking with a GUI, used widely in the embedded industry for ~40 years and still supported on some IBM point-of-sale terminals in the 4680 and 4690 range.

I wrote about the extended family:

https://www.theregister.com/2022/08/04/the_many_derivatives_...

MP/M was fairly common in small office environments. I remember one particular accounting firm which had managed to delete all their files on the harddisk.. they had an MP/M system with, IIRC, eight terminals connected. I managed to restore all their files (not very difficult on CP/M or MP/M, as long as the drive is left in peace after the incident, which is what they did).

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