Re: [stella] PAL VSYNC timings??

Subject: Re: [stella] PAL VSYNC timings??
From: Dennis Debro <ddebro@xxxxxxxxxxxxx>
Date: Tue, 19 Nov 2002 7:06:29 -0500
Hi Eric,
> Curious, Skeleton cycles it's PRNG and does some other things during VSYNC.
> Maybe a look at the Solaris & Desert Falcon disassembly might provide some
> hints.

I ran Solaris and Desert Falcon through Z26 to get a read out.

VSYNC stops on scan line 4 at cycle count 14. It also does not do 3 WSYNC lines. The last line of the vertical sync is done by instructions taking longer than 76 cycles on the previous line.

Desert Falcon:
VSYNC stops on scan line 3 at cycle count 2.

> My guess (based upon the NTSC docs I've seen) is enabling VSYNC causes the
> TIA to output the serration pulses (NTSC lines 4,5 & 6) which are low except
> for two pulses in the middle & end of the line.
> If this is true, then VSYNC needs to be enabled & disabled during the
> horizontal sync pulse period of the line.  So, as long as you do the STA
> VSYNC immediately after the STA WSYNC (and don't hit RSYNC while VSYNC is
> enabled) you should be okay.

I guess we need to find other games that tend to roll to further test your theory. Does anyone know of any others besides Solaris and Desert Falcon?

Take care,

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