28 Nov
2016
28 Nov
'16
7:51 p.m.
On 11/28/16 6:46 PM, william degnan wrote:
I don't believe this has any
specific diagnostic meaning. It's possible
that there is a stuck bit in the front panel logic. It's also possible
there is something wrong with the MMU, since (IIRC) the MMU is what
drives address bits 16 and 17 from the CPU side.
If you load an address from the front panel, is it *actually* loading
the address on the switches, or is it loading the address on the
switches with bit 16 also on? Try depositing a known word into a
specific memory address, like 1000 using the console PROM, then try
reading it back with the front panel.
- Josh
Recently
(today) I noticed Address light 16 would come on when I examine
an address. For example
All switches down, turn on machine (set to 000 000)
RUN/PROC/BUS/CONSOLE lights come one, all other lights off
hit LOAD ADDR
address light 16 comes on, RUN/PROC/BUS/CONSOLE lights stay on.
If I hit START light 16 turns off.
If I try again, to load an address, the address I selected appears, but so
does light 16.
I believe I have seen the explanation for this symptom somewhere, but
reading the 11/40 CPU manual and handbook and I could not find the
explanation. Does anyone know what this means?
I have been booting directly into the console, lately the system has no
problem loading and running from the console. Perhaps this huge missed
issue is the root of the problem I have been having get much else done.
Bill