Configuring an MS11-L for an 11/24

Chris Zach cz at
Sat Oct 17 21:26:16 CDT 2020

So I'm working on this old MS11-L board I have had sitting around 
forever. M7891 DK. Goal is to use it in my 11/24 with KT24 MMU.

I've switched the jumpers so it will run on a +12 supply instead of a 
+15, and so it will run in an extended Unibus slot as opposed to a 
normal unibus.

However I'm stumped regarding the +5v and +5 BBU supply lines. The 
problem is the manual says to set the jumper that is above C12 (bottom 
of board, two capacitors next to each other, pretty easy to spot) so 
that W3 is in and W7 is out if you just have +5v. On this board, W3 is 
out, W7 is in, but there are two other jumpers right above them (nothing 
is labelled on the board).


Is it the bottom jumper that is +5 or the bottom and the one above that 
need to be moved?

This might be why this board never worked right, if the memory refresh 
is expecting power on the BBU line and I don't have that then it's not 
going to work very much :-) But which jumper is the right one to use?


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