Question about Intel disk formats

From: Don Maslin <>
Date: Wed Jun 20 23:51:30 2001

On Wed, 20 Jun 2001, Vintage Computer Festival wrote:

> I've got some 8" disks that are apparently double density (the
> manufacturer label says so). I thought they were Intel ISIS formatted
> disks (which Eric Smith said would make them M2FM and uncompatible with
> anything other than an Intel MDS development machine) but I'm not so sure,
> since I can't seem to access any on the two Intel MDS systems I have set
> up.
> Both machines have Shugart 801 drives in them, and after doing some web
> research, I've come to find out they are single-density only. This would
> probably explain why I am not able to access these disks on these
> machines.
> The disks I am trying to access are supposedly CP/M, but the labelling
> indicates they were perhaps used on an Intel development system (they have
> filenames on the label with ".HEX" file types; this may not mean
> anything). If this is the case, and they were formatted on an Intel MDS
> (and therefore M2FM), and since they are double-density, then I may not be
> able to read them with the machines I have.
> However, I want to check their format on some CP/M machine and see if
> perhaps I can read them. If so, then they are probably more standard DD
> formatted diskettes, maybe even CP/M since that is what I was told they
> are.
> If they are in a standard DD format, and I have a computer that can boot a
> DD CP/M system master, could I then pop these disks in the drive and do a
> DIR to see if I get a directory?

Sellam, there is not really a 'standard DD format' in CP/M. There are
so many variations that if you tried that it would be a matter of purest
coincidence if it could read them.

> For those who've used these before: when I put any of the disks in
> question in the drive, the drive seems to seek for a few seconds, then
> goes off for a split second, back on again for half a second, then off
> (and the system crashes). The normal boot sequence for a (single density)
> system disk is, upon reboot the disk seeks for a few seconds, then stops
> for a split second, then starts seeking/reading for a few more seconds and
> the ISIS prompt comes up.
> It seems the system is trying to read the double density disks and just
> not seeing anything intelligible and crashes. With single density
> non-system diskettes, the machines will come up with something like "NOT A
> Suggestions appreciated.

You could mail me a couple and let me see if I can read them. Can't do
m2mfm, but most other.
                                                 - don

> Sellam Ismail Vintage Computer Festival
> ------------------------------------------------------------------------------
> International Man of Intrigue and Danger
Received on Wed Jun 20 2001 - 23:51:30 BST

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