Re: [stella] interlace

Subject: Re: [stella] interlace
From: Chris Wilkson <ecwilkso@xxxxxxx>
Date: Sun, 25 Jun 2000 03:01:19 -0400 (EDT)
On Sat, 24 Jun 2000, Eckhard Stolberg wrote:

> At 17:59 23.06.2000 -0400, you wrote:
> >Anyone remember why can't you do calculations during VSYNC?  I remember the
> >discussion (a couple years back), but I don't remember the details.
> It was probably me, who did most of that discussion. ;-) I noticed that
> some 60Hz NTSC games would roll on my PAL VCS/TV while most others worked
> fine. The games that rolled the screen all did something during the three
> lines of VSYNC. Sometimes it was only so simple things as setting up the
> timer for the VBLANK period between the second and third WSYNC.

Hmmm.  Weird.  So I was looking at some video on the scope tonight,
(exciting Saturday night, huh?) and it turns out the 3 lines of VSYNC
is enough.  But the VCS doesn't do the serration properly.  In my memory,
it was 6 lines of sync, but it's actually 3 lines, with an extra pulse
in the center of the line.  Hmm.  Waveforms, etc. will be forthcoming...
I need to find a scanner first.

BTW, are there any common games that roll?  I'd like to see what's
different about the video during VBLANK.


Archives (includes files) at
Unsub & more at

Current Thread