RE: SEGA to Amplifone converter

> I found David Shuman's info on building a converter to run
> SEGA vector games on Atari XY monitors, including a caveat
> that it can't seem to keep up when there are a lot of vectors
> to draw.

That more or less mirrors my experience. It was fine for testing and
tinkering, but I probably wouldn't want to use it as a final solution.

> David postulates that it's a bandwidth problem with the amplifiers.
> Could the cause be the slew rate of the WG6100? Since the
> Amplifone is faster, perhaps the converter would work 100%
> when using an Amplifone?
> Anyone have any experience running this setup?

I really don't remember what I did when I used my Wg6100 on the
SegaMultigame prototyping. I probably had something very similar to David's
circuit if it wasn't the actual one he posted. (The timing is quite
suspicious since that's about when I was working on the Sega Multigame, so I
probably saw his post and tried it.)

As I mentioned before in another thread, probably 98% of things looked fine,
but that 2% resulted in visible tearing. I mostly noticed it when there was
a large delta between points (not necessarily just when there was "lots" to
draw). I'd wager a guess that that was the fallout from GO8 being able to
reposition the beam faster than the WG6100 could. (In the Atari AVG's you
generally don't ever jump the beam more than half a screen width at a time,
so the SegaXY vector generator doing that probably exceeds the WG6100's
design spec.)

At the time I remember thinking that if you could essentially add a hardware
wait state in the G-80 system vector generator when there's a long beam jump
that it'd probably work 100%, but at the expense of a slight framerate hit
possibly. If I ever explored that further I don't remember what became of
it now. ;-)

Zonn will probably know off the top of his head, but I don't think it would
be any sort of bandwidth problem. I suspect it's just slew rate limited
with the WG6100's lower deflection voltages. It would be interesting to
find out if the WG6400 could keep up though.

-Clay

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Received on Wed Jul 15 00:15:12 2009