8" floppy system needed to recover old game data

[Allison]

>
>Subject: RE: 8" floppy system needed to recover old game data
>   From: "Kieron Wilkinson" <Kieron.Wilkinson at paretopartners.com>
>   Date: Thu, 06 Oct 2005 13:59:35 +0100
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>
>My reasons for suggesting doing a track dump is so we can leave figuring
>out the filesystem later... Which from my experience of other systems
>means it is less likely we would get it wrong "on the day". It is bad
>enough getting this done once, twice would not be too fun either. ;)
>
>But of course, CP/M is not exactly part of my previous experiences.

CP/M file system is fairly easy to understand.  It was fairly standardized
depite media variations.  A dump of any form would be reconstructable
if there are no lost sectors.

For 8" systems they fell onto two major groups:

Hard sector:  Altair and a Zilog used those.  However _most_ 
              hard sector 8" systems rarely carried CP/M.

Soft sector:  Most common and there was a standard interchange format
              for CP/M.  That was 8" single sided single density (8"SSSD).
              Other formats that existed were CP/M on Intel (M2FM) and
              Odd sector sizes or double density.  Likely formats in 
              the 8" realm were fortunatly fairly few (likely one of 5).
              The two most common after SSSD was SSDD (single side 
              Double density) and DSDD (double sided double density).
              The latter two SSDD  was often seen and had a fairly similar
              layout compared to SSSD.  The DSDD was far less common and
              there were a few different ideas how data should be laid down.

FYI: the M2FM (intel MDS) used conventional 8" drives but the FDC was really

 



The 5.25 worlds was chaotic as drive were developing and people needed to 
push those minifloppies from the base of only 80k to a more useable 360
or even 780k. Where the base 8"SSSD was 256k from day one.




>
>> A "photocopy" of a disk is possible using (MS)DOS, if you can 
>> find a MicroSolutions Compaticard IV (I have one, and no, I 
>> dont want to part with it).
>> This card works very well; I once generated a bootable MS-DOS 
>> 3.1 (or 3.20?) 8"
>> floppy.
>
>Nice.
>
>> The only (in my opinion) good solution, is software reading 
>> the CP/M (or
>> whatever) disk, and decode the filestructure etc., so you can 
>> write a nice, continuous file.
>
>Absolutely, my only concern was getting that wrong. But perhaps it is
>far simpler operation to work out the file system with CP/M than getting
>a track dump the disk, in which case this method is probably more
>appropriate.
>
>Of course one reason (off topic!) to dump the whole disk (down to the
>flux-transition level) is to ensure you get absolutely everything on the
>disk. But of course, this is only really useful for retail software that
>might have applied copy protection - not really applicable for a
>developers old development system! :)
>
>Thanks!
>Kieron
>
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