21 May
2009
21 May
'09
11:08 a.m.
I currently have the CPU boards + MMU option
installed in the correct
order with a SLU card in the SPC slot, and an M981 connecting to a
4-slot Unibus backplane with a single 64K MOS memory card (M7891) in
slot 2 -- all other slots have grant continuity cards installed. The
Unibus terminator is installed in the last slot.
Any ideas?
Normally when a system hanges if you had an M9302 terminator, it's a
grant problem (as I've mentioned before, if a grant actually gets to the
M9302, that card assets SACK, causing the CPU (or more precisely the
arbiter) to deassert the grant line. If the 'grant' is due to a signal
floating because of an open grant chain, the CPU can't deassrt the grant
line _at the terminator_, and the system hangs with SACK asserted).
Anyway, you mention you've got grant continuity cards in all the empty
slots. I assume the're in the right connector (D), and the right way
round :-). In which case, check the NPG jumpers on your backplane
(wirewrapped links from pin CA1 to CB1).
oriented such that the label "Grant
Continuity" is the right way up (or
put another way, such that the conductors on the card edge are facing
toward the back of the machine).
Correct.
I'll check the NPG jumpers -- here's a stupid question -- how do I find
where they're supposed to be? I've looked all over for a simple diagram
showing which pins are CA1 and CB1, but I'm not finding them...
OK. The 'C' means connector C (the one above the connector where you've
puy the grant card)
The 'A' and 'B' mean the top 2 pins on a particular side (the 18 pins on
a particular side are lettered A B C D E F H J K L M N P R S T U V)
The '1' means the front (component) side of the connector.
There should eb a wire-wrapped link between these 2 pins on every SPC
slot in the machine. It would be fitted at the factory, but cut if an NPR
(DMA, basically) device was used in that slot. In fact it _must_ be cut
if you put such a device in the slot.
-tony