Path: utzoo!utdoe!generic!pnet91!ericmcg
From: ericmcg@pnet91.cts.com (Eric Mcgillicuddy)
Newsgroups: comp.sys.apple2
Subject: Re: ASIC-65816 News
Message-ID: <444@generic.UUCP>
Date: 3 Feb 91 16:18:07 GMT
Sender: root@generic.UUCP
Organization: People-Net [pnet91], Etobicoke, ON
Lines: 28

>But isn't a faster CPU in effect an accellerator? Or how do they do it
>now? Sorry about the dumb question, but I really don't understand!
>
>Daniel Gross

How fast can a car go? 100 mph, 150mph? How fasst can it go in a school zone?
40MPH, 25? Just because something is capable running faster than allowable
doesn't mean that it will. You might want to consider modems also, if you have
a 9600 modem, but dial up a 300 baud board, you will only be able to D/L at
300. This is the bottleneck. 

Note that even with an accelerator your SYSTEM still only runs at 2.5MHz( or
1MHZ if doing I/O to disk). What the accelerator does is save often used code
and data in an area of very fast memory on its card (or in its chip in the
case of the Zip Chip). It can run all of the stuff here at full speed, but
must slow down to normal if the code or data it needs is not present in this
memory. It is a fact that 20% of the code of any given program is executed 80%
of the time that the program is running. Keeping that 20% in the memory cache
letsyou run the program as fast as physically possible, the trick is finding
the right 20%. The Zip isn't too bad, with a 16k cache 8Mhz is a little more
than twice as fast as a stock GS, about the equivalent of 6MHz.

The 25Mhz ASIC chip would be around 20MHz, or about 8 times faster. Assuming
that this is shipping speed and not maximum attainable with immersed in liquid
nitrogen.  :)

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