jackrubin
Veteran Member
Everything you need to know is at Glen's website - https://sites.google.com/site/glensvintagecomputerinfo/home . I'm sure he'll chime in here momentarily.
Jack
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Is SCSI boot an option for PDP-11/53?
- Thread starter acollins22
- Start date
gslick
Veteran Member
There are /M, /T, and /TM versions of the CQD-200 and CQD-220, which can do MSCP only, TMSCP only, and both MSCP and TMSCP at the same time. The CQD-223 is the same as the CQD-220 except it is mounted in a quad wide carrier with S-handles for a BA200 type chassis.
The CQD-220 has some additional firmware features over the CQD-200, such as the ability to split a single SCSI LUN into 2 or 4 MSCP units. Also I believe the CQD-200 lacks the ability to maps to non-zero SCSI LUNs. For example a single SCSI device with 4 LUNs could be mapped to 4 different MSCP units on the CQD-220 while you can't do that on the CQD-200. I haven't poked at mine in a while so I am not 100% sure on those details. I don't know if there are any performance differences between the CQD-200 and CQD-220. For the most part a CQD-200 should work just a well as a CQD-220 in a Q-Bus PDP-11 system.
The CQD-220A has /TM and /E (or /M/T) versions. The /TM version can do both MSCP and TMSCP at the same time while the /E version can be configured to do Either MSCP or TMSCP, but not both at the same time. The CQD-220A should have all of the firmware features of the CQD-220. I don't know if it has any performance improvements over the CQD-220.
Physically the CQD-200 and CQD-220 boards are fairly similar while the CQD-220A switched to mostly surface mount components and some of the logic was replaced by a large ASIC. The CSR address decoding is done in a PAL on the CQD-200 and CQD-220 while it is done in the ASIC on the CQD-220A.
Roe
Experienced Member
Got it. Thanks. I knew about the /T, /M, and /TM versions. I was not aware that the 200 couldn't do LUN splits, which I definitely require.
gslick
Veteran Member
I never updated the CQD-220A information there with what I found out about the PAL.
On the CQD-200 and CQD-220 the CSR and MSCP vs. TMSCP decode is done in the PAL and I am pretty sure I reverse engineered that correctly.
On the CQD-220A I think the CSR decode must be done in the ASIC for the standard choices, except for the special disk mode and special tape mode choices in the CSR address selection tables in the manual. Those CSR decodes do come from the PAL and CMD probably provided customized PALs on request if necessary. Other than that the PAL appears to have an output code indicating whether the board should be a /TM or /E version (which is the thing you would want to change to convert a /E version to a /TM version, along with the firmware) plus some other pins that had no function that I could determine. I tried an /E version converted to a /TM version and it appeared to work as expected although I was never 100% sure about reverse engineering the PAL.