Progress on NEC APC

From: Don Maslin <>
Date: Fri Apr 21 16:03:57 2000

On Fri, 21 Apr 2000, Fred Cisin (XenoSoft) wrote:

> On Fri, 21 Apr 2000, Tony Duell wrote:
> > > DIR but they all come back with "NO FILE". Now of course this means
> > This message is also telling you a couple of good (?) things. Firstly
> > that the drive/controller is managing to read valid sectors off the disk
> > (so the drive is working, the heads are clean enough to read something,
> > etc). Otherwise you'd be getting the well-known BDOS errors.
> Also, by not getting error messages, that it's finding the sector numbers
> that it's looking for, therefore it has the expected number of bytes per
> sector and range of sector numbers (do the numbers start at 0, 1, 20, ...)
> I just checked, and the NEC 8" CP/M diskettes that i"ve seen have 256
> bytes per sector; but not the MS-DOS ones, therefore I retract my previous
> suggestion that these might be MS-DOS diskettes.

True, it is finding the sector numbers it is looking for, but it also is
finding E5H where it expects to find the user area number or there could
be either an error message or perhaps a garbaged directory display if it
found 00H by chance.
> > And secondly the directory makes some sense as a CP/M directory. At least
> > the system thinks it does, and it thinks its empty. So it's likely (not
> > certain ) that the disks are CP/M86 ones.
> Definitely not CERTAIN. An empty CP/M directory is indistinguishable from
> a blank formatted track, and similar to empty MS-DOS directory sectors.

But MS-DOS does not use E5H and does use 00H fill in directory areas. I
suspect that this might confuse the CP/M-86 directory program a bit - a
whole bunch of null filled directory entries, all at user 0!

                                                 - don

> Since CP/M had reserved track(s), the CP/M directory would miss the FAT,
> and could easily occupy sectors at the end of an MS-DOS directory. MS
> Stand-alone-BASIC, which was used on a lot of NEC products, but which I
> haven't seen on the APC, had a directory similar to the Coco on a middle
> track; the track used by CP/M for its directory could be empty. The NEC
> 8" CP/M diskettes that I've seen have had several different numbers of
> reserved tracks; therefore it could be a CP/M format, but not the RIGHT
> one.
> > I think one option to the STAT command (STAT USERS, STAT [USERS] ???)
> > will tell you at least which user numbers have files on the disk
> Do you have any communication with the makers of the disks? Is THEIR APC
> working? If so, try STAT DSK: on both machines and compare.
> --
> Fred Cisin
> XenoSoft
> 2210 Sixth St. (510) 644-9366
> Berkeley, CA 94710-2219
Received on Fri Apr 21 2000 - 16:03:57 BST

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