Re: 10 mhz 6502's...

["Roger Johnstone" <rojaws@mac.com>]

In article 
<Pine.GSO.3.95.iB1.0.1010830021049.7467A-100000@halifax.chebucto.ns.ca>,
Tony Cianfaglione <ab616@chebucto.ns.ca> wrote:

> On Wed, 29 Aug 2001, Wayne Stewart wrote:
>
>> Plugging a faster chip into any Apple II won't do anything. Quite a few of
>> the
>> IIes I've enhanced have ended up with 4mhz 65C02s (because thats what I
>> had
>> on hand) and run happily at 1mhz.
>>
>>     Wayne

> If that's true, what made the ZipChip so special - a different design?

The Zip Chip is actually made from four chips. It has a faster 65C02
processor, a pair of cache chips and a custom gate array. Instead of
packaging each chip and then soldering them to a board they connected the
bare chips together (which are tiny) and put them in one package. The only
disadvantage is that it's impossible to upgrade or service it.

Since the Apple II motherboard can't be run faster than 1MHz the Zip Chip
reads the Apple II main memory at 1MHz and stores it in the cache RAM chips.
The fast CPU, running at 4 or 8MHz, can access the cache chip at full speed.

--
Roger Johnstone, Invercargill, New Zealand

Apple II - Future Cop:LAPD - iMac Voodoo2 - Warcraft II
http://homepage.mac.com/rojaws
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