Path: utzoo!utdoe!generic!pnet91!ericmcg
From: ericmcg@pnet91.cts.com (Eric Mcgillicuddy)
Newsgroups: comp.sys.apple2
Subject: Zip GSX
Message-ID: <554@generic.UUCP>
Date: 3 Mar 91 16:15:05 GMT
Sender: root@generic.UUCP
Organization: People-Net [pnet91], Etobicoke, ON
Lines: 21

A while back people were talking about the ASIC 65816 clone and installing a
20MHz version on the ZIP GSX. The discussion revolved around the fact the Zip
GSX controller is designed to run at 20MHz out of the box.

This is NOT true. The controller is designed to run at a 40MHz crystal speed,
but this must be divided by 4 for the card to function. This gives an absolute
maximum speed of 10MHz. To get faster, effectively the board needs to be
replaced. I suspect that you can push many of the components beyond their
rated speeds, but the failure rate will increase significantly.

The good news is that 10MHz is now available. It is expensive, but available.
With a 64k cache this makes it almost twice as fast as a 7MHz TWGS
(unconfirmed, but so reported).

BTW the hit ratio seems to be in the neighbouhood of 60% with a 16k cache,
increasing the cache is about the cheapest way to improve performance. I
expect that a 64k cache will produce close to 90% hit ratio. Although I would
prefer 256k myself.

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