Re: Apple emulators that support "floating bus" video sensing?

[Dirk Thierbach <dthierbach@usenet.arcornews.de>]

Michael J. Mahon <mjmahon@aol.com> wrote:
> If we assume that the emulator is supposed to emulate an Apple II
> with an accelerated *processor*, 

But to get "correct" behaviour for most programs, one shouldn't assume
that. If a program uses the "vapourlock" to adjust its own timing so
it can do tear-free updates of the framebuffer, or switch pages once
during a frame, that one should emulate exactly this behaviour.  Which
means that the value read from the floating bus depends on the cycle
count, not on real time, and that the way the emulator updates it's
own video from the frame buffer should also depend on the cycle count
(which isn't too hard to do if the emulator use some double-buffering
scheme, though it would involve a substantial change to probably every
emulator).

> As it is, it emulates an Apple II with both the processor and the
> video refresh accelerated--and there is no such beast!

Look at it differently -- it just emulates an Apple II with both
processor and video refresh at the same (normal) speed. It's just that
the outside world (the humans who interact with it) happen to be a bit
slower :-) After all, time is relative...

- Dirk