VSYNC problems (was: [stella] Thomas Jentzsch's PAL -> NTSC Conversions)

Subject: VSYNC problems (was: [stella] Thomas Jentzsch's PAL -> NTSC Conversions)
From: Thomas Jentzsch <tjentzsch@xxxxxx>
Date: Sat, 9 Feb 2002 09:42:00 +0100
At 09.02.2002, 00:29, Roger Williams wrote:
>> Gas Hog is setting up a timer and keeps polling it constandly.
>> Indy 500 also does that, and I had problems with this game
>> too

> This absolutely will not work with video hardware that times
> from the end of VSYNC instead of the beginning.  There will
> be variations in the timing which are not acceptable.  The point
> of writing to WSYNC is that the end of the pulse is timed
> exactly to within one cycle.  When you set up a loop you
> get at least a 15-cycle, and sometimes more, variation in
> the length of the pulse.

I understand, but Gas Hog does an WSYNC before turning of VSYNC too (see
my previous post). So that can't be the reason here.

Have fun!
Thomas Jentzsch         | *** Every bit is sacred ! ***
tjentzsch at web dot de |

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