Re: How does the ZIP chip work?

[Eric Smith <eric@brouhaha.com>]

Bryan Parkoff wrote:
>     Do you mean that 6502 / 65C02 CPU chip are limited to 1MHz according to 
> the CPU design?

No, they're limited to 1 MHz due to the Apple II design.

> If you rewire 6502 CPU to 14M crystal osc by modifying 
> timing logic, it might work without accelerator card.

Not if you want your Apple II to actually work.  The other logic and
memory chips in the Apple and on peripheral cards are not fast enough,
so nothing would work correctly.

But even if the electronics otherwise worked, you wouldn't get proper
video, because all the timings would be approximately fourteen times too
fast.  Your horizontal and vertical sync would be around 220 KHz and
840 Hz, rather than around the required frequencies of 15.75 KHz and 60 Hz.

And even if all that worked, you'd have to rewrite RWTS and any sound
routines.