Re: IIgs RGB to VGA experiment

["mdj" <mdj.mdj@gmail.com>]

Michael J. Mahon wrote:

> No, you'd need a voltage regulator--but that's not a problem.
>
> As mentioned above, changing the operating voltage of the whole
> board is not the best way to adjust sampling frequency.  ;-)

I'm surprised there's not a trimpot on the board of the device to
adjust its sampling frequency.

Could this be a result of the IIGS not outputting it's signal at
exactly 60Hz ? I'd expect that whatever technique the device uses for
conversion, it would need to synchronise the vertical refresh of the
output to the input to avoid rolling, tearing, or other effects. If the
IIGS is a little off, the device would have to compensate its
horizontal scan rate accordingly. Connecting to a TV may not be a good
way to determine the IIGS behaving exactly according to its
specifications.

I'm assuming that such a device either buffers one or two scanlines
(harder) or an entire display sweep (easier) in memory, then reoutputs
it at as close to VGA'ish frequency it can manage, while remaining
synchronised with it's input.

Of course, this is guesswork based on how I'd build such a device
myself - the actual device might operate completely differently, though
somehow I doubt it. 

Matt