Re: SRAM on ZipGSX - how fast for 14MHz?

[Wayne Stewart <waynes@intergate.bc.ca>]

Rodney Hester wrote:

> Right now I'm trying to push a ZipGSX to 13.75 MHz with a 55 MHz oscillator.
> I've already done the 74HC00 mod successfully.  I'm running 15ns tag RAM and
> 20ns data RAM, with zero stability.  It won't even finish booting.  Swapping
> for a 40 MHz oscillator (the next closest I've got) cleans up everything
> nicely, as does (usually) putting both 15ns SRAMs in the first (32K) banks,
> flipping the jumper to 32K cache, and cranking down the speed a notch or two
> with the Zip CDA while running the 55 MHz oscillator.
>
> Should I have purchased even faster SRAM?  I can get 12ns chips, but I think
> that's the fastest that is readily available.  For those who have a ZipGSX
> running comfortably at 14 MHz, what speed SRAM are you using?  I'd just like
> to try to gauge if I'm encountering a non-SRAM problem here.

I'm at 15mhz using 15ns cache in both data and tag. I likely would have gone
for faster
SRAM but that was the fastest I could find locally. Keep in mind though that
the 15ns
rating just means that that's just a minimum speed rating. I have some other
brands of
15ns SRAM that wouldn't get me over 13.5mhz stabily.

    Wayne