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

[Roy Miller <millers@inebraska.com>]

Wayne Stewart wrote:

> 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.

I have a Zip like yours (only I have 64K of SRAM), and, like you, I can't push my
Zip past 10 mhz.
What's really sad is I bought a 14 mhz chip to replace a 10mhz chip. I could have
stayed where I was....

Roy

>
> >
> > 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