Hi folks,
An M9301-YB bootstrap terminator that I’ve been using during the restoration of
a PDP-11/45, which has previously worked fine, now seems to be failing on me.
Examining the contents from the front panel I see a few words with different
values than the ones that Noel has listed in his partial M9301-YB disassembly.
A question for Noel if he’s listening here: how did you obtain your YB listing,
and would you consider it reliable? That is, would you think it reasonable to
try blowing some replacement PROMs based on that listing? I have seen no other
source for the YB contents online anywhere else.
There is a note in the M9301 Operator’s Manual about the layout of the PROMs -
words split into 4 bit fields programmed in all the PROMs in “parallel”, lower
8 bits inverted to support extra invert in the switch circuitry, and
higher-addressed bank in the lower-half of the PROMs. 512x4 tri-state parts.
Anybody have any particular part recommends for the PROMs? I haven’t been able
to find engineering drawings for the M9301 online so far to check the original
PROM part numbers, either.
I may also have a go at writing a program I can toggle in to read the contents
of my failing M9301 and dump them out over the console serial to enable a
systematic comparison with Noel’s listing.
cheers!
—FritzM.
