Progress on NEC APC (fwd)

From: Dwight Elvey <elvey_at_hal.com>
Date: Fri Apr 21 19:52:50 2000

>>>>> Forwarded message from Don Maslin <donm_at_cts.com>



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

> On Fri, 21 Apr 2000, Don Maslin wrote:
> > > what the CP/M-86 would see on the MS-DOS format.
> > It gives you a big fat error message.
>
> In THIS case, due to sector size differences. But not ALWAYS. I have
> seen non-CP/M disks with E5 where a CP/M directory would have been.

I don't recall running across that, but I'll be alert now.
 
> MS-DOS will give a big FAT :-) error message when trying to read CP/M
> (actually "Probable Non-DOS disk") because it is picky about what it
> expects to see in the F.A.T.

Agreed.
 
> Due to reserved tracks, on 8" double density, CP/M's DIRectory will
> fall AFTER the end of the MS-DOS directory, where the first file would
> otherwise be likely to be. You're right that that would almost certainly
> be content that would choke CP/M. But with very short files and large
> clusters, and with sector interleave, it is entirely possible to have CP/M
> looking at unused sectors.

Possible, but...
 
> Both MS-DOS and CP/M will accept and assume "empty" when encountering
> a DIRectory (not the MS-DOS F.A.T.) sector of all E5. MOST MS-DOS formats
> fill the empty directory sectors with 00, but not all. Some use E5, some
> F6 with E5 every 32 bytes, ... What would CP/M-86 report for a directory

Rather like a CP/M directory that had its files deleted :)

> sector of all 00? An MS-DOS format with a large directory could easily
> leave the END of the MS-DOS directory sectors where the first of the CP/M
> directory sectors would be.

Agreed. I'll have to try the 00 bit and see what does actually
happen. I'll let you know.
 
> I don't often see use of USER in CP/M disks. Sometimes, but not often. I
> think that it is more likely that they gave Sellam blank formatted
> diskettes.
 
I wouldn't argue that. On the other hand, it would be prudent to check.
If he would mail one or more of the disks to me, I could examine them
and probably provide an answer.
                                                 - don

<< End forwarded message
Received on Fri Apr 21 2000 - 19:52:50 BST