Wanted: Info on Optisys/Optidisk WORM file system

[Chuck Guzis]

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the world, being superseded by rewritable media (both CD-RW and MO).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