11 Feb
2021
11 Feb
'21
9:31 a.m.
I have a bunch of Panasonic/Matsushita 470/940 MB phase-change WORM
discs here--and the appropriate drive (Panasonic LF-5010 SCSI-2) to read
them.
Unlike CD-R media, however, the format of these discs is not anything
standard--they were essentially treated as hard disks. So, adding a
file involves copying the directory and then adding the file information
to the copy. The same applies, of course, for file deletion. If the
drive tries to read a (1,024 byte) sector that hasn't been written to,
it will get an error after a number of retries. I should emphasize that
this drive is *not* fast--throughput seems to be on the order of a
floppy disk.
I can probably (with a bit of head-scratching) figure out the
methodology behind this system, but I'm giving a shout-out to see if
this rings any bells. Phase-change WORM did not enjoy a long life in
the world, being superseded by rewritable media (both CD-RW and MO).
As a point of reference, here's the data from sector 1 of a sample disc
(Sector 0 is not used):
00000400 04 0d 04 16 00 0f 0a fe 02 00 20 03 00 03
48 47 |.......... ...HG|
00000410 49 42 32 2e 31 31 2d 30 33 2e 30 30 43 72 65 61 |IB2.11-03.00Crea|
00000420 74 65 64 3a 20 54 68 72 20 32 32 20 41 70 72 20 |ted: Thr 22 Apr |
00000430 31 39 39 33 20 20 20 20 20 31 35 3a 20 32 2e 32 |1993 15: 2.2|
00000440 38 3a 35 31 20 20 20 20 4f 70 74 69 73 79 73 20 |8:51 Optisys |
00000450 4f 70 74 69 44 69 73 6b 20 28 43 29 20 43 6f 70 |OptiDisk (C) Cop|
00000460 79 72 69 67 68 74 20 31 39 38 37 20 2d 20 31 39 |yright 1987 - 19|
00000470 39 31 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |91 |
00000480 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
If nothing turns up in the community, I'll work out the format and make
details available (as I understand them).
TIA
--Chuck