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marmotking
April 30th, 2010, 08:26 AM
I have a couple of VAX 11/750's that I'd like to get running. I have some memory boards for them and the appropriate memory controllers. However, I seem to have a variety of suffixes on the memory boards. Does anyone know the difference between them all? For example, what' different between M8750-CD and M8750-CB or M8750-CF? They're all 1MB boards, right? Can they be mixed on the same machine? Thanks!

pontus
May 3rd, 2010, 01:45 AM
I have a couple of VAX 11/750's that I'd like to get running. I have some memory boards for them and the appropriate memory controllers. However, I seem to have a variety of suffixes on the memory boards. Does anyone know the difference between them all? For example, what' different between M8750-CD and M8750-CB or M8750-CF? They're all 1MB boards, right? Can they be mixed on the same machine? Thanks!

Cool! I also have one 11/750, not running. My guess is that the letters are just different revisions and that they should go together.

Here is a nice link:
http://home.claranet.nl/users/pb0aia/vax/750faq.html

I also think you should join the classic computing mailing list which has a lot of people with vax knowledge. And at least one who is currently restoring a vax 11/750. Why not start by searching the archives:

http://www.classiccmp.org/pipermail/cctalk/

/Pontus

smj
May 24th, 2010, 07:35 PM
For example, what' different between M8750-CD and M8750-CB or M8750-CF? They're all 1MB boards, right?As I'm sure you've found out by now, they should all be the same capacity and should all work together -- assuming these particular boards work, period.

For future reference, with regard to memory boards the -XY notation's first letter usually indicates the capacity of a board -- the M7608-AA is a 2MB memory board while the M7608-BA is a 4MB board. The second letter will indicate a different revision, or sometimes in the case of memory cards a different supplier of the main RAM chips. I'm not clear if there's a uniform standard for how these notations are used with cards other than memory boards, for example the M7516 DELQA vs. M7516-PA DELQA-S vs. M7516-YM DELQA-M. And in all likelihood any such conventions probably changed over the decades that boards were being given MABCD designations.

When in doubt, rely on a source like the Field Guide to Qbus and Unibus Modules - a Google search may be a more durable trail for future reference, but I tend to use the copy Megan Gentry maintains here: mbg's genuine draft (http://http://world.std.com/~mbg/pdp11-field-guide.txt).