On Mon, 04 Sep 2000, you wrote:
> > Interrupts must be disabled during waiting and the timeout value must be
> > smaller than 1/60th of a second.
>
> Music (games/apps) and Modem (apps) won't be happy with that.
The good news is, that using a non-timed protocol interrupts can be allowed.
It must be done carefully, because too many or badly timed interrupts will
kill performance, but at least interrupts no longer influence correctness.
> It requires a timer on both sides running both at the same speed. Which you
> haven't, unless both have a MusicModule or OPL4 plugged in (timings of MM
> and OPL4 are slightly different, so they have to be equal on both machines),
> and then the transfer rate will still be very slow compared to synchronous
> communication and the entire concept of JoyNet (cheap, easy) will be lost.
Shevek wanted to use instruction length for timing at first, but now he
agrees that this is too problematic.
Note that you cannot even trust two timers of the same kind to run equally
fast. For example, start a music replayer in two MSXes with the same song at
the same moment. After about a minute you'll hear that they're out of sync.
So even 60Hz isn't exactly the same for every MSX.
We should indeed remember that the whole point of JoyNet is to be simple and
cheap. If we want high speeds, we'll need different hardware. I'm interested
in that, but it's a different project.
> I do have ideas on how to implement a bidirectional
> peer-to-peer link using JoyNet (=2 computers only).
Let's hear it! Supporting more than 2 nodes is a matter of routing, and it
can be solved in a higher layer.
> As far as I can see, it's also not possible to communicate bidirectional
> using a JoyNet network (>2 computers), since it has only 1 dataline (ack)
> going back to the previous host (for acknowledgement), and the other two
> datalines (dat1 and dat2) go to the next host.
Without fixed timing, bidirectional transfers are indeed impossible over
JoyNet.
> However if you have every
> host connected to two others using a peer-to-peer link (2 computers, so not
> really a 'network') in both joystickports (which make it a network again),
> then bidirectional transfer is indeed be possible.
The idea of JoyNet was to keep one joystick port free. For example, to play a
game using a joystick or game pad.
Bye,
Maarten
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