22 Jun
2001
22 Jun
'01
2:20 a.m.
If it is CP/M standard format, it should be IBM3740 formatted single-density.
There are lots of other formats that work under CP/M though. I've never seen a
format with an identifying signature that was recognizable on another system.
However, since different systems have different controllers, they use different
approaches to using that controller. Interleaving rates are a common
inconsistency between systems, but 4 is a common interleave for double-density
with a 4 MHz Z80. You can get some insight into the way data layout is
implemented if you look at the directory track (track 2). If there's a
recognizable file name, then you can rigorously search for the data that
comprises that file by searching the entire diskette. If you don't have the
interleave, it doesn't matter, since directory entries are in 128-byte sectors,
derived from the Single Density format. All you need is the name of a widely
known standard file, e.g. PIP.COM. You then find the file contents, bit by bit,
and keep records of where you found each 128-byte block of the file, and then
divine the sector layout from that. It's not fun, but you only have to do it
once.
Good luck!
Dick
----- Original Message -----
From: "Edwin P. Groot" <epgroot(a)ucdavis.edu>
To: <classiccmp(a)classiccmp.org>
Sent: Thursday, June 21, 2001 6:55 PM
Subject: Re: Question about Intel disk formats
If it is CP/M format, the first track should be
SD, whether or not the
disk is formatted DD. That's how it is in the CP/M systems I have. I
figure you should at least be able to read the first track and hopefully
there would be a signature of what machine it's from. What I would not
know is what interleave factor to use for the sector ordering; it seems to
vary from machine to machine. Start with the original IBM SSSD structure.
Edwin
At 08:31 PM 6/20/2001 -0700, you wrote:
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.
Suggestions appreciated.
Sellam Ismail Vintage Computer
Festival
---------------------------------------------------------------------------
---
International Man of Intrigue and Danger
http://www.vintage.org