Parity Error on Motherboard (???)

[Kaleb Keithley]

This is a last ditch effort, before I go out and replace my motherboard.

I just added four more meg to my (generic Taiwan) 386SX motherboard, bringing
it to a total of eight meg.  The machine boots, memory test finds no errors, 
but both my protected mode operating systems, OS/2 1.1 and ESIX 3.2.C, crash.
Good old M'soft provides the wonderfully intuitive "Parity Error ????", 
while ESIX says "PANIC: Parity Error on Motherboard" followed by a dump 
message.

By taking the two SIMMs out of the fourth bank, everything works ok.  I
swapped all eight SIMMs around in the first three banks, so I know they're
all good.  I only get the parity error when I plug SIMMs into the fourth bank.

Anyone have any thoughts?
-- 
Kaleb Keithley                      Jet Propeller Labs
kaleb at thyme.jpl.nasa.gov

"So that's what an invisible barrier looks like!"