On Sun, Jan 31, 2021 at 5:05 PM Fritz Mueller via cctalk <
cctalk at classiccmp.org> wrote:
ZAP is effectively reset for the micro-architecture, forcing the ucode
address to known/initial value. It has multiple sources throughout the
processor, including tendrils into some of trap handling hardware. (Caveat:
my experience is based off extensive work with the '11/45, but the
micro-architecture as I understand it for the '11/70 is quite similar.)
Yeah, ZAP seems to be the entry point at power-up as well as for trap
For the '45, there was a very handy "KB11-A,D
Maintenance Manual", which
explained the logic of such internal signals and the board by board
internal operation of the CPU to a very useful level of detail; I'm sure
similar is available for the KB11-B,C? It's worth a read through if you
haven't already, though its quite a bit to take in.
Yes, there's a similar doc. The engineering drawings include the flow
diagrams for the microcode, and the Processor Manual (
goes into details on the rest. I started digesting all of this last night,
it's going to take awhile :).
I would imagine the next step would be to throw the RAC board out on
extenders, verify that ZAP is asserted, and if so pursue the driving source.
Yeah. I want to get the fans installed and then go triple-check all the
power signals and get the voltages dialed in nicely. But then things come
out on extenders :).
Do you know if you have a KB11-B or C?
It's a KB11-C.
Thanks, it'll be interesting for sure.