4 Jan
2002
4 Jan
'02
7:35 a.m.
--- Tom Leffingwell <tom(a)sba.miami.edu> wrote:
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.
Have you checked the jumpers on the M8059? Where in memory does it think
it is supposed to live? Even the M8044 has address jumpers.
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.
Yes, I would expect that your backplane is 18-bit. It wouldn't matter,
anyway - 18 bits is 256Kbytes (2^18 = 262,144) or 128Kwords. The 128K
card will fill your memory space, but it should work on an 18-bit
blackplane. You can also stuff 4 M8044 cards in there - 32Kwords each
for a total of 128Kwords.
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?
Is it on the maroon handle? I don't think it's anything in the solder
mask/copper; there might be an ink stamp with the revision or perhaps a
sticker. If you can't tell in anyway, shape or form, perhaps you have
a rev A.
Also, is possible to modify the 18-bit bus and make
it 22-bit, or
maybe by swapping out the backplane?
You can run the extra backplane wires. I have done it. Having done so,
you may have to find a way to terminate them. Newer boxes are already Q22
and have bus termination built-in. Older backplanes depended on a
termination card - the BDV-11 is one that is termination plus bootstrap
ROMs.
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?
I forget the characteristics of each backplane type in the BA-11 series
off the top of my head, but some of the 9-slot backplanes are all Qbus,
some are 50% Qbus and 50% CD slots (with a board-to-board interconnect on
the C and D fingers) which you need to use certain peripherals (the two-
card RLV11 RL01/RL02 controller comes to mind immediately; the RLV12 is a
Q22 controller on a single card).
Different configurations, different features, different prices.
Hope this clears things up.
-ethan
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