PDP-11/45 RSTS/E boot problem

Noel Chiappa jnc at mercury.lcs.mit.edu
Mon Dec 31 22:43:32 CST 2018

    > From: Paul Koning

    >> On Dec 31, 2018, at 6:32 PM, Henk Gooijen via cctalk <cctalk at classiccmp.org> wrote:
    >> ...
    >> There are one or two bits in a register of the RK11 that have a
    >> different meaning/function, depending on the controller being a -C or
    >> -D.

    > If someone can point me to the description of the differences I should
    > be able to say what RSTS will do with them.

AFAIK, the only difference (in programming terms) between the -C and -D is
that the -D has dropped the maintainance register.

Although I cheerfully admit I haven't sat down with -C and -D manuals and
done a bit-by-bit compare. I just did that (I used the "RK11-C Moving Head
Disk Drive Controller Manual", DEC-11-HRKA-D, and the 1976  "Peripherals
Handbook"), and found in the following:

In the RKDS: bit 7 has changed the definition slightly ("Drive Ready" to
"R/W/S Ready"), but seems to be basically the same. In the RKCS, bit 9 is
"Read/Write All" in the -C, and unused in the -D; bit 12 is "Maint" in the
-C, unused in the -D.

In other words, a -D driver should work just fine with a -C, IMO.


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