RE: C128 and 8MHz Z80
Date: 2002-07-29 04:25:57

Hi Nicolas,
(apologies for not making comment earlier)

>Recently I got something that might be quite interesting: a small PCB that
>boosts the Z80 in the C128 to 8MHz. It has the name Rossmöller on it, this
>the same company that made the C64 Turboprocess 4MHz card. 
>The PCB has a GAL on it, and it has two wires: one gets the 8MHz dotclock
>from the 8701, the other an 1MHz signal from one of the bus buffers (I
>for synchronisation of memory accesses). The GAL also connects to the
>previously unused Z80 signals that control memory access and wait states.
>it can run at 8MHz unless it needs memory access, while in the original
>it uses 4MHz during one half of a 1MHz cycle (does anyone know if it can
>both 1MHz cycles in fast mode?).

Could you identify which chips/pins these other wires go to? Do you think
that this would be a easy way to also engineer a faster 65802 CPU into the
C128? In the past I tried doing something on the by multiplying the clock
phase on the 8502 side, but as the RAS and CAS signals are produced by the
VIC it would crash. How does the Z80 get away with it?

- Nick


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