> Actually... On the 2600, you need to be able to respond instantly to
> controller input. Not all games simply check it once per 50/60 Hz frame,
> with the obvious exception being anything that reads the paddles. Have
> a paddle read miss by even one scanline (0.0063 milliseconds), and the
> onscreen paddle missed the ball on one machine and not the other, and
> there goes any hope of synched emulation.
The game might need to read the input more than once per frame, but
the emulators sure don't have to. ;-) In z26 for example we generate
a paddle value once per frame that specifies after how many scanlines
the capacitor should be recharged. Whenever the game reads the paddle
input we compare this value with the scanline number and set the port
bit accordingly. Transfering this value once per frame should be enough
to maintain the same state on both emulators.
> I don't think peer-to-peer emulation is even possible. Client-server
> certainly is, which must be what Nesticle and all the other emulators
> capable of it are doing.
One emulator sure has to be the master that selects the ROM image
and all the other settings and that starts the actual emulation, but
from then on it should be possible to have two emulators running in
sync, provided that the computers are fast enough and that the connection
allows a stable 60 Hz transfer speed, I think.
Ciao, Eckhard Stolberg
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