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DECMate II vs. DECMate III WPS disk structure.

Chuck(G)

Chuck(G)

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On the RX50 disks used in both the DECMate II and III there appears to be a substantial difference in recording format.

The DM II WPS records 12 bits out of 16, but DM III WPS appears to not clear 4 bits in the second byte. For example:

DM II WPS:
Code: 
00001400  00 00 02 00 08 08 08 e7  00 01 00 00 00 00 00 00  |................|
00001410  00 00 ff 09 ff 09 ff 09  ff 00 28 00 31 00 21 0a  |..........(.1.!.|
00001420  2b 04 2b 0b 0e 07 2b 08  14 0a 07 04 3a 0a 44 0b  |+.+...+.....:.D.|
00001430  32 00 ed 0d 2c 0a c0 0e  ec 0d 11 0a 08 0f 11 06  |2...,...........|
00001440  1a 0b 10 02 0f 06 29 06  29 0a 2b 08 0e 07 23 0a  |......).).+...#.|
00001450  c5 0e 31 02 49 06 20 0e  07 06 01 0e 06 06 44 0b  |..1.I. .......D.|
00001460  c7 0e 49 02 e9 0d d5 0e  06 02 2b 08 06 06 c1 0e  |..I.......+.....|
00001470  2b 08 2b 08 80 00 00 01  49 02 e9 0d 15 0a 12 00  |+.+.....I.......|
00001480  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
[/code}

DM III WPS:
[code]
00001400  00 00 02 00 08 08 08 e7  00 01 00 00 00 00 00 00  |................|
00001410  00 00 ff 79 ff 79 ff 79  ff 70 28 20 31 30 21 2a  |...y.y.y.p( 10!*|
00001420  2b 24 2b 2b 0e 07 2b 28  14 1a 07 04 3a 3a 44 4b  |+$++..+(....::DK|
00001430  32 30 ed 6d 2c 2a c0 4e  ec 6d 11 1a 08 0f 11 16  |20.m,*.N.m......|
00001440  1a 1b 10 12 0f 06 29 26  29 2a 2b 28 0e 07 23 2a  |......)&)*+(..#*|
00001450  c5 4e 31 32 49 46 20 2e  07 06 01 0e 06 06 44 4b  |.N12IF .......DK|
00001460  c7 4e 49 42 e9 6d d5 5e  06 02 2b 28 06 06 c1 4e  |.NIB.m.^..+(...N|
00001470  2b 28 2b 28 80 00 00 01  49 42 e9 6d 15 1a 12 10  |+(+(....IB.m....|
00001480  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

Am I reading this correctly? Note that the block header bytes are the same in both cases and, in particular note the byte stream at offset 70h:

Code: 
DM II:
2b 08 2b 08 80 00 00 01
DM III:
2b 28 2b 28 80 00 00 01
Is this due to a missing instruction in the write loop of the DM III?
 
wonder if that's why the wps278 images i was using never worked on my dmii?
 
Well, I'll play with my conversion code to clear the extra bits and see what happens. I've got about 50 of these DM III WPS disks, so no lack of sample space.
 
Added a couple of lines of code to strip out the garbage nibble in my conversion routines and it works just like the DM II, example:

Code: 
There is no charge for this two day event.  Participants will be housed 
in the newly rebuilt and redecorated facilities used primarily for the 
Advanced Management Program and the International Senior Managers 
Program.  The opening lecture will commence at 5:00 p.m. on Monday, 
September 8, and the program will end at lunch time Wednesday, September 
10.

I hope that you will be able to attend.  We are limiting participation to 
80 people, and priority will be given in the order of response to this 
letter.  Please respond, using the enclosed card, as soon as possible if 
you wish to participate.

Apparently just that simple--no change in disk layout.
 
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