PDP-11 memory question

From: Tom Leffingwell <tom_at_sba.miami.edu>
Date: Fri Jan 4 15:09:59 2002

        I have a PDP 11/23 (M8186 CPU with floating point and MMU options)
in a 4 slot BA11-MA box that at some point in its life was an 11/03. It
had an M8044-DF 32k memory module, which I'm trying to replace with a 128k
M8059-KJ. The system works fine with the 32k module, but won't do anything
with the 128k module. I'm not familiar with PDP-11's, but it seems like
my backplane is only 18-bit, while the new memory module is 22-bit. I've
also read that the M8186 board is only 22-bit compatible after revision
C. I can't find any mark on the board showing what revision it is. Is
there another way to tell?

        Also, is possible to modify the 18-bit bus and make it 22-bit, or
maybe by swapping out the backplane?

        I also noticed that on some used PDP-11 web sites that the BA11-M
sells for much more than the BA11-S, which I thought had 5 more slots.
Is there some reason for this?

Thanks,

Tom
Received on Fri Jan 04 2002 - 15:09:59 GMT