Re: second processor on a II:How?

[david@zircon.cs.uow.edu.au (David E A Wilson)]

dpscholn@mtu.edu (Dan P. Scholnik) writes:
>: Anyway, your 6809 won't tell you when its not using the buses, like a 
>: Z80 does (with individual read and write lines, and dynamic refresh lines.)

>	Actually, the 6809 BA line is high when the processor busses are
>tristated. Plus, they are inactive in the first half cycle like the 6502.

Correct. The Stellation Mill 6809 card for the Apple // uses this capability.
The 6809 runs at full speed and the 6502 gets the left overs (approx 20% of
bus cycles). There are just a few instruction sequences on the 6809 that have
to be avoided - they have no dead cycles and the 6502 forgets.