Re: C128 and 8MHz Z80

From: David Wood (
Date: 2002-07-09 12:55:43

Even if the GAL is security-locked, you can trip each I/O line and see if
you can get a dependable pattern.

Could you glance at the underside of the pcb and detail what lines go where? 
It can help with some educated guesswork on how the gal's used. ;)


On Tue, 9 Jul 2002, Nicolas Welte wrote:

> 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 is
> 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 guess
> for synchronisation of memory accesses). The GAL also connects to the
> previously unused Z80 signals that control memory access and wait states. So
> it can run at 8MHz unless it needs memory access, while in the original C128
> it uses 4MHz during one half of a 1MHz cycle (does anyone know if it can use
> both 1MHz cycles in fast mode?).
> I'd like to run some Benchmark tests on this thing, are there any standard
> programs for CP/M I should use?
> I also need to get that GALBlast built (have all parts already), maybe the
> GAL isn't security fused and I can read it out.
> BTW, I have a picture of the device online:
> Nicolas
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