Difference between revisions of "Victor 9000 format"

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Revision as of 20:02, 2 March 2011


A very strange format used by the Sirius One / Victor 9000 computer. This machine ran MS-DOS and CP/M, but had a very unusual disc format:

  • Variable speed -- 9-zone Z-CLV. The linear velocity of the disc is held fairly constant by rotating certain blocks of tracks slower than others, and storing more data sectors on the outer ("longer") tracks.
  • GCR coding -- specifically, a 4-to-5 GCR code which looks like MFM on a timing histogram.

Other than that, they're pretty standard. A DiscFerret can accurately sample and (in theory) decode these discs.

Low level format

GCR code table

From the source code to CW 0.13 by Karsten Scheibler:

input (hex) output (bin) output (hex)
0 01010 0x0a
1 01011 0x0b
2 10010 0x12
3 10011 0x13
4 01110 0x0e
5 01111 0x0f
6 10110 0x16
7 10111 0x17
8 01001 0x09
9 11001 0x19
A 11010 0x1a
B 11011 0x1b
C 01101 0x0d
D 11101 0x1d
E 11110 0x1e
F 10101 0x15