Re: 10 mhz 6502's...

[Roy Miller <millers@inebraska.com>]

Supertimer wrote:

> "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.

Have you done that?
I'd be interested in hearing from someone who has....

Roy

> 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.