[Simh] Custom ROMs on PDP-11 sim

[Christian Gauger-Cosgrove]

On 16 December 2017 at 19:20, Tim Stark <fsword007 at gmail.com> wrote:
> Well, there are some PDP-11 tech docs indicates that higher models like
> 11/53, 11/73, 11/74, 11/83, 11/84, 11/93, and 11/94 have built-in own
> firmware ROMs at starting 160000 with switch bits for banking.
>
Don't include the 11/74 in that list, as it's the SMP 11/70 derived
Beast of a machine.

Per Micronote 039 the KDJ11-B boards (M8190) has bootstrap/diagnostic
ROMs, which covers certain models of 11/73, but does cover the 11/83
and 11/84. The KDJ11-E (M8981) of the 11/93 and 11/94, and the KDJ11-D
(M7554) of the 11/53 also have on board boot ROMs.
The KDJ11-A (M8192) boards which are also called PDP-11/73, do not
have ROMs; for them you need to use an MXV11-B (possibly with it's
memory disabled; enjoy board surgery), an MRV11-D ROM module, or a
22-bit upgraded BDV11 bootstrap/terminator card (ECO Rev. E, I
believe).

I've not looked at the bootstrap ROMs of the KDJ11-B, KDJ11-D, or
KDJ11-E, but I know the information for the MRV11-D and BDV11. In the
BDV11 the bootstrap ROMs "live" at 173000--173777 and which of the 256
words (512 bytes) are mapped into that space is controlled by the PCR
at 177520 (the lower byte lets you set which page 173000--173377 is
mapped to, the upper byte of the PCR controls 173400--173777; there
are maximum 256 possible 128 word pages). In the MRV11 the bootstrap
ROMs "live" at two different windows, 173000--173777 (as with the
BDV11) and 165000--165777; the PCR lives at 177520 (as with the
BDV11). The PCR is split into controller two 512 byte windows
separately (window 0 is the one at 173000 and window 1 is at 165000);
however there are only 7 bits available (highest order bit of each
byte is ignored) so the maximum possible is 128 512B pages mappable.

I've not looked at the MXV11-B documentation, but the MRV11-D is
specifically mentioned to be compatible with MXV11-B boot ROMs so I
would assume it would work similarly.

Cheers,
Christian
-- 
Christian M. Gauger-Cosgrove
STCKON08DS0
Contact information available upon request.