CP/M disk format: need help - test-drb@ccmp.vtda.org

27 Dec 2011

On 12/27/2011 01:40 PM, Enrico Lazzerini wrote:
...
  Well this is all i know:

 8"

 STAT d:DSK:

 9600

 r:  128  Byte  Record  Capacity

 Thats 1.28mb!  Not many system used that and some like DEC RX02, Intel 
MDS DD
were not MFM ( both were unique oddbal that most FDCs do not read).

...
  1200

 k:  Kilobyte  Drive  Capacity

 128

 d:  32  Byte  Directory  Entries

 128

 c:  Checked  Directory  Entries

 128

 e:  Records/  Extent

 16

 b:  Records/  Block

 64

 s:  Sectors/  Track

What format are you trying to achieve??   Looks vaguely like Morrow DD.

...
  2

 t:  Reserved  'rracks

 2

 SIDES

 This is that I calculate:

 BEGIN SCO2 (1024 bytes/sector) - DSDD 8"

 DENSITY MFM ,HIGH

 CYLINDERS 77 SIDES 1 SECTORS 8,1024

 SIDE1 0 1,2,3,4,5,6,7,8,9

 SIDE2 0 1,2,3,4,5,6,7,8,9
 Likely does not start with sector 0, that is unlikely due to the bit 
pattern and how DD controllers work.

Besides 0 though 9 enumerates 10 objects, not 8.

...
  ORDER CYLINDERS

 BSH 4 BLM 15 EXM 3 DSM 599 DRM 127 AL0 0C0H AL1 0 OFS 2
 Looks about right.

There is no skew applied as you show it.

If skew is wrong reading the directory is impossible and you get trash 
if anything at all.

Allison
...
  END

 Here what 22disk tell me:

 http://elazzerini.interfree.it/Foto2982.jpg

 Where I'm wrong?

 Thanks for any suggestion.

 Enrico