Re: [stella] Overscan

Subject: Re: [stella] Overscan
From: Erik Mooney <emooney@xxxxxxxxxxxxxxxx>
Date: Wed, 21 Jun 2000 21:57:28 -0400
>The 2600 (as with most game systems until recently) fool the TV into 
>displaying full-width fields instead of true interlacing.  This results in 
>half the effective vertical resolution but without the interlace 
>flicker.  It doesn't really just display duplicate fields becaue the net 
>effect is no black space inbetween fields.  It's turned into 60fps 
>progressive scan.
>I don't understand how it manages to do this, though.

Somebody explained it a while back (loooong time ago) as such:
Interlaced NTSC is actually 525.5 lines for two fields.  The extra 0.5
line is what causes the TV to move the next field down 0.5 scanlines,
which generates the interlace.  If somebody can figure out a way to make
the TIA generate half a scanline (by which I mean count 114 color clocks
after WSYNC and then start generating another horizontal sync), and do
that every other field, you should get a true 30fps interlaced display.
The only possible mechanism would be RSYNC, which still nobody has gone
to experiment with (don't look at me, I haven't the time or interest

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