CP/M for the C-64

[dpatten]

I was going through my C-64 stuff to day, preparatory to getting the machine set back up and imaging my games and High school papers to PC. In amidst the game diskettes (Gyruss!) was a shoebox. Opening it up, I discovered a bunch of utility and nibbler disks and wonder of all wonders, a disk labeled Commodore CP/M and a manual.

I vaguely remember my dad bringing the box of disks home when I was in high school from a co-worker who had upgraded to an Amiga. Apparently the guy was on of the founding members of our local "el-shift-oh" Commodore user's group in the mid '80s

Looking through the manual I saw that a z-80 expansion unit is necessary to use CP/M.

My question is, Is it even worthwhile to try this? I'm guessing the program uses the 6510 to bootstrap the Z-80. What kind of memory would be left over? 20-30k? wouldn't the 1541 drives wonky track setup with variable sectors wreak havoc with standard CP/M software?

The idea of a C-64 running CP/M sounds awesome, but is it really worth it?

 

[Zeela]

No it's not really worth it.
You'd need an CP/M cartridge expansion and as for memory, you have 48K available to CP/M the rest is used by the C64 Kernal and such. The Z80 is underclocked to be able to use the C64 memory bus.
The screen size is only 40 cols so it would be hard to use any applications using 80 cols (I guess CBM CP/M implements some sort of scrolling sideways, but that's just annoying)
As it uses the 1541 all disks needs to be in CBMDOS format so that the drive can read them.

If you really want to run CP/M on a Commodore machine, try the C128 with a 1571. It runs CP/M 3 or plus or whatever it's called. And the 1571 drive is able to use most floppy formats.

Some links on the topic:
http://www.z80.eu/c64.html
http://www.scribd.com/doc/16061442/Commodore-64-CPM-Operating-System-Users-Guide

 

[Dave Farquhar]

The other thing about CP/M on the 64 was that the cartridge wasn't compatible with all 64s. I think the trouble was in the VIC-II chip.

If you want to actually use CP/M a little, Zeela is right, a 128 is better. Even on the 128, CP/M isn't terribly fast, but you can make it usable. It's reasonable when booting off a 1581 and your favorite apps running from a 1750 RAMdisk. There are also a couple of Von Ertwine's free utilities that let you tweak CP/M's internals a bit to speed things up. But I was less happy with CP/M on the 128 after I saw it running on a Kaypro box.

I suspect that you'll be using CP/M as a novelty, more than actually sitting down and trying to do a lot of work with Dbase and Wordstar. So if you can find an early enough 64 that's compatible with the cartridge, you'd be able to fire it up, come back in 20 minutes, and show off one of the world's slowest CP/M boxes.