Re: ZipGS stability at 15 MHz - update

[wbaguhn@nyx10.cs.du.edu (Will Baguhn)]

In article <8JUL199617432544@vax2.concordia.ca>,
Mitchell Spector <spec@vax2.concordia.ca> wrote:
>   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

Hmm... what are the speeds of those SRAMs?  You didn't happen to damage
the trace at J8, did you? (perhaps for a split-16k cache?)

The faster SRAMs should always go in the TAG sockets.  It may be that you
have a toasted upper-half of the cache.  if so, only one may be toasted...
process of eliminiation should show you which chip.

good luck.
-- 
                                      --- SPQR (wbaguhn@nyx.net)