13 Nov
2006
13 Nov
'06
5:49 p.m.
Gooijen, Henk wrote:
Just 2 boards left from the point where I started, the
Quadrasync E
and the second memory board. I chose to install the second memory
board first. Power on ... RUN led stays ON (!), console printout is
not what it should be, allthough a prompt appears when I hit ^P.
Entering "d 1000 55" returns the "?Halt CP" message.
When I remove that second memory board all is back to "normal"!
By first
memory board I infer that you mean the MS11-M M8722 256KB.
This board requires both +5V for logic and +-12V for the memories.
By second memory board I infer that you mean the MS11-P M8753 1MB.
This board is 5V only; it does not require either +-12V or +-15V.
I would have expected it to be the other way around (MS11-M does not
work but the MS11-P does) but hey. It could be a stuck driver on the
MS11-P that is pulling some memory/unibus control signals to ground,
hanging the bus and cpu.
I have not had the time to add the Quadrasync E board (leaving the
2nd memory board out of the system of course, and I have not yet
made any measurements ... I know, I should!
But I start guessing that the +/-12V perhaps has an issue. That
might explain (?) the problem when the 2nd memory board is added,
Not sure about
that; if the 2nd memory board is the MS11-P, then it
only uses +5V, so it should have no interaction with +/-12V.
but why is the first memory board OK? Perhaps just the
logic on
that 2nd memory board died, and hangs the system (not the UNIBUS
as the memory is *not* on the UNIBUS!).
Note, the 2 memory boards are different, but the system was in
productive operational condition at a company in that configuration.
The +/-12V "issue" (if there is one) also might explain why the
FAULT light is always ON on the RL02.
That was also in perfect order till a week ago ...