Re: Faster IIe

[Scott.Alfter@skunkworks.genesplicer.org (Scott Alfter)]

In article <2844078@f10.n209.z1>,
Shawn T Beattie <sbeattie@cs.iastate.edu> wrote:
>I have noticed that the 65C02 in my Apple IIe has the following
>printed on it:
>
>G65SC02P-2
>
>I assume that means it is a 2Mhz 65C02.  Is there any hardware
>modification that could me made to the motherboard that would 
>allow the 2 Mhz speed to be realized?

Nope.  Assuming that the CPU is a 2-MHz part, the likely reason that
Apple chose it is that they wanted to make sure that the CPU would be
done with a memory read or write in 500 ns or less.  The CPU is
clocked at 1 MHz, but memory is accessed at a 2-MHz rate because
memory access is interleaved between the CPU and the video hardware
(when the CPU isn't using memory, the video hardware is reading it to
refresh the display; one side effect of this technique is that DRAM
refresh is done alongside video refresh).  For more details, you might
want to grab a copy of the _Apple_IIe_Technical_Reference_Manual_.

Scott Alfter