Re: Apple// CP/M question

[dempson@actrix.gen.nz (David Empson)]

Paul Schlyter <pausch@saaf.se> wrote:

> In article <1ek4vqw.1wr445s1vyinmcN%dempson@actrix.gen.nz>,
> David Empson <dempson@actrix.gen.nz> wrote:
> 
> > Roy and/or Janet Miller <millers@inetnebr.com> wrote:
> > 
> >> Paul Schlyter wrote:
> >> 
> >>> 2. Even if Apple // disks had been compatible with the rest of the
> >>> world on the sector level, MSDOS still uses a different logical disk
> >>> format than CP/M.
> >> 
> >> The fact is that there was no standard disk format for CP/M on 5.25"
> >> disks, or for that matter the occasional machine that used 3" or 3.5" inch
> >> disks.
> > 
> > We have a CP/M kitset machine at work (in a suitcase!) which we used
> > actively until about 1990, and have occasionally used since then.
> > 
> > It has 8" and 5.25" drives.  The standard CP/M disk format was a single
> > sided single density 8 inch disk (40 tracks, 128 bytes per sector, but I
> > forget how many sectors per track: possibly 32, which would make it 160
> > KB).
> 
> The 8" SSSD format was 128 bytes/sector, 26 sectors/track, 77 tracks
> of which two tracks were "system tracks" where the boot loader and the
> BIOS+BDOS+CCP was stored.  This yielded 243.75 KBYtes of user area per
> disk including the directory, and 241.75 KBYtes excluding the directory.

Ah, that sounds more like it.  I thought the disk capacity was in the
ballpark of 250 KB.  I hardly ever touched these disks, so didn't look
into the format in detail.

Thanks for the correction.