Re: Zip-GS speed and cache

[rubywand@aol.com (RUBYWAND)]

In article <4nn4ce$221c@enzu.unm.edu>, casa@unm.edu (Jim Pittman) writes:

>....
>I called Digi-Key and they said they had 32-mHz crystals. So I can get
>a new crystal and slow the Zip down to 8-mHz. But -- if it runs okay at
>9.3 mHz and 8-k cache, am I better off than I'd be at 8-mHz with 16-k?
>Is the odd 9.3 mHz speed likely to cause any problems? (Digi-Key said
>they could not supply a 36-mHz crystal for exactly 9.0 mHz speed.)
>
>Or, could I get four different (presumably higher speed rating) memory
>chips and run at 9.3 mHz and either 16-k or 32-k or 64-k cache? If so,
>what chips would work?

     If forced to choose, you would be better off at 8MHz and 16K cache.
Going to 32K cache is worth the extra expense.

     Before ordering a bunch of faster RAM IC's, you might try swapping
the current RAM IC's. If the card still works with 8K cache and not 16K
cache, then the speed bottleneck may be in the address decoding or
somewhere else besides the RAM.

     John Link did a series of articles on accelerator card speed upgrades
for Appleworks Forum. He claims that the 45ns RAMs on the Zip-GS should
work okay up to around 12.5MHz. (A 10MHz Zip-GS with 64K cache has four
MCM6206P45 RAM chips.)  If the difference in cost does not seem too great,
get 35ns RAM chips for expanding your cache. 

     If the uP, RAM, and other IC's are 'fast enough', then running at an
odd frequency should be okay.

     Probably, your best move is to get the 32MHz oscillator from
Digi-Key. If everything works, then you can be pretty sure that the board
is performing as per specs. If you then want to add cache RAM or
experiment with higher speeds, it will be from a well-defined 'square
one'.

Rubywand