federico@actisb.UUCP (Federico Heinz) (06/03/91)
First of all, thanks to everybody who answered my query. I tried out
every suggestion, but none of them worked. I finally tried out a crazy
idea that popped up in my mind at about 3:00 am (while I was
sleeping), and that solved the problem. As it turns out, you CAN mix
parity and non-parity memory on the 68040 board, but only if you mix
them THOROUGHLY.
But first, the disclaimer: I don't know what I'm doing. I'm a software
type, and although I can set up an RS232 cable, even that smells of
black magic to me. Maybe what I'm about to suggest is slowly frying my
motherboard as I type this, so try it out AT YOUR OWN RISK. If your
system goes up in flames, don't blame me, I'm probably already crying
over the ashes of my system.
I found out that, if you mix parity and non-parity memory in a bank,
the system will think that the whole bank is non-parity, and it then
lives happy with the SIMM salad. I plugged the SIMMs in the following
order (P=parity, N=non-parity):
N N P P N N P P N N P P N N P P
and the system booted fine. I'm puzzled about why this works, but it
does. I'm even more bedazzled at the fact that the system wouldn't
boot with 8 MB parity memory either---maybe both boards I tried out
were broken after all, but I resist the idea.
Maybe this should go in the FAQ? Not many people are asking it yet,
but I fear they're coming.
--
Federico Heinz (federico@actisb.uucp)