On 3/12/2022 3:20 PM, David Schmidt via cctech wrote:
I have some disks that look like they're from a DECmate II computer,
standard RX50K drives. The disk images all look like they're a mix of
12-bit (OS/78 or OS/278?) and 8-bit all on the same media. I can't
convince PUTR to make sense of the images, so I'm wondering if there is
anything else out there that is likely to be able to examine the disk
contents? I'm really looking for PUTR-like functionality to list and copy
files.
Since it's a DECMate II, these may be WPS disks.
At least for the RX01/RX02, Those are 8-bit mode except for the boot
sector (because the standard boot was for a 12-bit mode disk.) I don't
know the layout for the RX50 - since it's not using the RX boot, there
shouldn't have been a need for a 12-bit boot sector.
It's also possible they're COS-310 disks, which also were 8-bit mode.
Using byte mode allowed WPS and COS to use the full capacity of the
disks. Apparently the RX50 controller retained this wasteful 12-bit mode.
Maybe SIMH could be configured to be a DECmate II and be fed the disks?
SIMH doesn't have an emulation for the RX50 controller on the DM2.
There's probably a different interleave being used here, so decoding the
layout would be a matter of trial-and-error.
The specs for the RX50 controller are available -
http://www.bitsavers.org/pdf/dec/pdp8/cmos8/DECmate/Decmate_II_Specification_Jan83.txt
That means that an emulator is possible.
-Rick
