--- Tom Leffingwell <tom_at_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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Received on Fri Jan 04 2002 - 15:35:20 GMT