Re: EightyOne

cheveron@xxxxxxxxx wrote:
I have seen some documents which seem to indicate that the AY is
clocked independently of the CPU in both the 128 and the 2068. However
I have no evidence for this one way or the other. And in practical
terms the actual value is so close to the one achieved by halving the
CPU clock that it probably makes no difference.

FWIW the TS2068 technical manual says that the AY clock is 1.76475 MHz (source not specified) and the Z80 clock is 3.528MHz (derived from a divide by 4 chain attached to a 14.112MHz clock).

Fuse uses a AY frequency of 1.764 MHz for this machine as I don't see where the extra 750Hz comes from and I am sure they would just generate the AY clock from a divide by 8 chain attached to the master clock. I can't see two crystals to source the clock on a photo of the PCB (but to be fair I don't see the master one either!).

For the (TC2048-derived) I believe that Yarek wouldn't have added a separate clock in order to drive the SE AY chip when he could derive the clock like on every other Sinclair machine :) (see <http://8bit.yarek.pl/upgrade/zx.ay/index.html> for schematics), so I am sure this machine has a 1.75MHz AY clock.

Fred
.

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