PDP-11/05 microcode dump?

Noel Chiappa jnc at mercury.lcs.mit.edu
Sat May 7 20:36:12 CDT 2016

    > From: Mattis Lind

    > What about compatibility between different revisions? I.e. Is it
    > possible to mix DataParh board and Control board from different
    > revisions with different microcode?

Well, I don't recall seeing any mention of compatability in the manuals, but
that is not definitive either way. I had a look at the two versions of the
data path board, and it seems to me that they are basically identical in their
interface and function, so that either version would work with any control
board version.

I looked at the interconnects with i) the other CPU board (on the C-F
connectors), and ii) the front console (through the Berg connector), and as
far as I can see, both boards use the same interconnects. I didn't track down
every last pin, and check them all, but I checked many, many pins, and all
the ones I checked were the same.

The two versions don't seem that different, internally. The PROMs are the
same on the two versions of the data path board, for what that's worth -
which is probably not that much. (The PROMs on the data path board don't
contain any microcode at all; that's all on the control board.)

One major difference is that the register file chips on the older board
(which have tri-state outputs, and use that to do a mux) have been replaced
by different register file chips, and real mux chips; however, the two
versions should work identically. There are differences in the area of the
serial line clock, but those should be immaterial.

There are some other minor differences, but again, it seems like they should
also work identically. So, that's the source of my conclusion that the two
versions of the data path card are functionally identical, and can be


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