Re: 10 mhz 6502's...

[supertimer@aol.com (Supertimer)]

"Roger Johnstone" <rojaws@mac.com> wrote:

>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.

That's right.  In the Apple IIc Plus, all the parts are discrete chips
but the design was from Zip Technology which Apple paid to use.
On the IIc Plus, you could actually upgrade the speed by changing
the oscillator just like on the ZipGS.  Unlike other Apple II models,
the IIc Plus has a "Zip" oscillator in addition to the clock that the
rest of the motherboard runs at so upgrading the CPU chip and
changing its clock won't mess up I/O.

The Laser 128EX/2, which was a IIc Plus competitor, took a very
different approach.  The whole motherboard ran at 3.6Mhz, CPU
and all.