59 ms·

Having fun with CP/M on a Z80 single-board computer

79 points by stevekemp 6y ago

jstanley 6y ago
> Add paging to TYPE Not really the same, but you might find that Ctrl-S/Ctrl-Q provides software flow control just like in Linux. I'm not sure if that's universal in CP/M, but it seems to be implemented in the CP/M BDOS on my RC2014 (RomWbW), at least.
- tyingq 6y ago
  A couple of other text viewers for CP/M: https://techtinkering.com/articles/text-viewers-on-cpm/ https://techtinkering.com/articles/text-viewers-on-cpm/
  - stevekemp 6y ago
    Thanks for the link, I've added QL(41) to my system now, and it's a cute little tool.
- stevekemp 6y ago
  Yeah that works, but timing it is hard. For the most part I run "TYPE BLAH", then use the history available to GNU Screen to scroll backwards in pages.
  - whartung 6y ago
    That's because you're running on a I/O device at 2 Billion Baud, instead of a 9600 baud device which is more era appropriate. At 9600, ^S/^Q is quite manageable.
    - anthk 6y ago
      Doesn´t any modern terminal emulator cap to 115200 anyways?
tyingq 6y ago
"It must run CP/M. The source-code to "everything" must be available." Interestingly, that's only been possible with CP/M relatively recently. Reading over http://cpuville.com/Code/CPM-on-a-new-computer.html http://cpuville.com/Code/CPM-on-a-new-computer.html you'll see he had to fix some OCR errors, translate 8080 ASM to Z80, etc. And it's still not really legal due to some poor wording in the last license: http://www.cpm.z80.de/license.html http://www.cpm.z80.de/license.html
- anthk 6y ago
  A pity CP/Mish is not more developed.
- VLM 6y ago
  zsdos is cpm software compatible and GPL licensed The closest analogy I can come up with is freedos is to msdos as zsdos is to cpm.
  - anthk 6y ago
    Does it run on the altair sim? any, the one from Simh, altairz80, or anything else.
    - tyingq 6y ago
      It's listed for this altair simulator: https://schorn.ch/altair_4.php https://schorn.ch/altair_4.php
      - anthk 6y ago
        But that doesn't replace the whole CP/M I think, just the shell. EDIT: I already mentioned altairz80, so I knew that page, indeed. The last time I tried a replacement I had the same issue: there is no libre CP/M 2.2 a la FreeDOS, at least fully compatible for the Altair.
        tyingq 6y ago
tasty_freeze 6y ago
> Since CP/M 2.x has no concept of sub-directories It has the notion of user areas. Each file entry has a 4b field tagging the file indicating which user space it belongs to. When you type "DIR" for example, it will filter and show only files for the current user space. There are no protections across user spaces. Typing "USER n" will change the current user space you are in. Although one could use it to allow multiple people to have a file space on one floppy, often it was used by a single user to partition work, eg, USER 0 is utilities, USER 1 is word processing, USER 2 is source code, USER 3 is games. So with a little squinting, it is possible to view CP/M has having 16 subdirectories, but the file system is flat in each subdirectory.
- whartung 6y ago
  The cold hard truth, however, is that CP/M is kind of awful. Back then you didn't have directories and subdirectories, what you had were floppies and disk drives. These were your file management components. Hard drives were rare, and CP/M was just not very friendly to large disk spaces. User areas had a marginal affect at the time, since they were really considered more apt to their name "User area", as in "separate users", vs a mechanic to actually organize files. Out of the box CP/M had really poor support for user areas. The simple fun fact that the way you shared a command across user areas was to...copy the file in to each user area. Which is easier said than done. The file copy program, PIP, could copy files FROM one user area to another (i.e. pull a file from one user area in to your current one), but not TO another user area. So, in order to copy files in to a user area, you had to have a copy of PIP in that user area. But you can't use PIP to move PIP in the first place. You have to jump through hoops loading PIP into memory with the debugger to span user areas. Later, new shells and utilities supported the idea of A3:FILE.TXT to represent user area 3 on drive A, started becoming common, but not every program supported it, and the stock OS did not support it either. Recall, in CP/M, the programs did most of the heavy lifting for this stuff. It's unjust, honestly, to criticize CP/M looking backward. It managed to empower great things back in the day, which is what microcomputing was all about. Its influence is felt to this day. But that doesn't necessarily mean it was a great place to be.
  - teh_klev 6y ago

79 points by stevekemp 6y ago

> Add paging to TYPE Not really the same, but you might find that Ctrl-S/Ctrl-Q provides software flow control just like in Linux. I'm not sure if that's universal in CP/M, but it seems to be implemented in the CP/M BDOS on my RC2014 (RomWbW), at least.

tyingq 6y ago
A couple of other text viewers for CP/M: https://techtinkering.com/articles/text-viewers-on-cpm/ https://techtinkering.com/articles/text-viewers-on-cpm/
- stevekemp 6y ago
  Thanks for the link, I've added QL(41) to my system now, and it's a cute little tool.
stevekemp 6y ago
Yeah that works, but timing it is hard. For the most part I run "TYPE BLAH", then use the history available to GNU Screen to scroll backwards in pages.
- whartung 6y ago
  That's because you're running on a I/O device at 2 Billion Baud, instead of a 9600 baud device which is more era appropriate. At 9600, ^S/^Q is quite manageable.
  - anthk 6y ago
    Doesn´t any modern terminal emulator cap to 115200 anyways?

tyingq 6y ago

"It must run CP/M. The source-code to "everything" must be available." Interestingly, that's only been possible with CP/M relatively recently. Reading over http://cpuville.com/Code/CPM-on-a-new-computer.html http://cpuville.com/Code/CPM-on-a-new-computer.html you'll see he had to fix some OCR errors, translate 8080 ASM to Z80, etc. And it's still not really legal due to some poor wording in the last license: http://www.cpm.z80.de/license.html http://www.cpm.z80.de/license.html

anthk 6y ago
A pity CP/Mish is not more developed.
VLM 6y ago
zsdos is cpm software compatible and GPL licensed The closest analogy I can come up with is freedos is to msdos as zsdos is to cpm.
- anthk 6y ago
  Does it run on the altair sim? any, the one from Simh, altairz80, or anything else.
  - tyingq 6y ago
    It's listed for this altair simulator: https://schorn.ch/altair_4.php https://schorn.ch/altair_4.php
    - anthk 6y ago
      But that doesn't replace the whole CP/M I think, just the shell. EDIT: I already mentioned altairz80, so I knew that page, indeed. The last time I tried a replacement I had the same issue: there is no libre CP/M 2.2 a la FreeDOS, at least fully compatible for the Altair.
      - tyingq 6y ago

tasty_freeze 6y ago

> Since CP/M 2.x has no concept of sub-directories It has the notion of user areas. Each file entry has a 4b field tagging the file indicating which user space it belongs to. When you type "DIR" for example, it will filter and show only files for the current user space. There are no protections across user spaces. Typing "USER n" will change the current user space you are in. Although one could use it to allow multiple people to have a file space on one floppy, often it was used by a single user to partition work, eg, USER 0 is utilities, USER 1 is word processing, USER 2 is source code, USER 3 is games. So with a little squinting, it is possible to view CP/M has having 16 subdirectories, but the file system is flat in each subdirectory.

whartung 6y ago
The cold hard truth, however, is that CP/M is kind of awful. Back then you didn't have directories and subdirectories, what you had were floppies and disk drives. These were your file management components. Hard drives were rare, and CP/M was just not very friendly to large disk spaces. User areas had a marginal affect at the time, since they were really considered more apt to their name "User area", as in "separate users", vs a mechanic to actually organize files. Out of the box CP/M had really poor support for user areas. The simple fun fact that the way you shared a command across user areas was to...copy the file in to each user area. Which is easier said than done. The file copy program, PIP, could copy files FROM one user area to another (i.e. pull a file from one user area in to your current one), but not TO another user area. So, in order to copy files in to a user area, you had to have a copy of PIP in that user area. But you can't use PIP to move PIP in the first place. You have to jump through hoops loading PIP into memory with the debugger to span user areas. Later, new shells and utilities supported the idea of A3:FILE.TXT to represent user area 3 on drive A, started becoming common, but not every program supported it, and the stock OS did not support it either. Recall, in CP/M, the programs did most of the heavy lifting for this stuff. It's unjust, honestly, to criticize CP/M looking backward. It managed to empower great things back in the day, which is what microcomputing was all about. Its influence is felt to this day. But that doesn't necessarily mean it was a great place to be.
- teh_klev 6y ago