ZipGS stability at 15 MHz - update

[spec@vax2.concordia.ca (Mitchell Spector)]

   A few weeks ago, as some of you may recall, I replaced my 8/16 ZipGS
with a 15/64 model. This immediately caused lock-ups and I suspected my
powersupply, especially since disconnecting a few slot cards and all my
floppy drives helped a great deal. I was still experiencing problems
however, and had decided to purchase one of those Buggie 150W supply, 
which incidentally is in the mail.

   Today I tried something in the meantime, I toggled the DIP switch
setting on the card so half of my cache is disabled. I'm running the
Zip in a 15/32 (32K cache) configuration. What's interesting is since
doing so my IIgs has been _completely_ stable. What's even more surprising
is I reconnected my floppy drives (what caused immediate lock-ups before) 
and it still continues to run fine! This is with my stock 60W supply.
Another oddity, when in the 15/64 confifuration, "Test Drive II" had
large gaps and lines going through sprites (and other areas of the
graphic screen). Now that I've disabled the upper 32K of cache, this
problem has disappeared.

   What is at fault here? Could it be some of the SRAM chips are
defective? I'm starting to wonder if a strong powersupply isn't
going to help once I switch the card back to 64K cache.

Mitchell Spector
spec@vax2.concordia.ca