Re: IIc+ accelerator

[a_specto@alcor.concordia.ca (Mitchell Spector)]

On 28 May 2001 10:23:57 -0700, aiiadict@hotmail.com (Rich J.) wrote:

>Hi,
>
>I could open my IIc plus to figure this out, but it is packed away.
>
>How does the IIc+ accelerator work?  Is it all on the CPU chip, or
>are there chips on the motherboard which help acceleration (slow down
>for I/O, cycle stretch, etc) ?

    It has the exact equivalent of a 4 MHz ZipChip. It was by no
coincidence though, Apple licensed the technology from (then)
Zip Technologies to use their patented acceleration technique 
within the IIc Plus. Technically it _is_ a Zip Chip inside.

    Though instead of an actual (tall) 40-pin ZipChip however, Apple
broke out the accelerator into separate components and incorporated it
into the motherboard. It consists of an ASIC, 65C02-4, two 8K SRAMs
(one for TAG and one for Data) and probably some other chip logic to
make it all work. It's been several years since I've last opened my
IIc Plus and had a look...

>Can I pull the CPU from my IIc+ and accelerate an apple IIe?

    No. You could pull the 4 MHz 65C02, but the IIe would just
run it at a standard 1.024 MHz frequency (in fact most 65C02's 
I've come across in stock IIe's are rated for around 4 MHz and
underclocked).

Mitchell Spector
a_specto@alcor.concordia.ca