Re: [stella] Cosmic Ark scanline pixel doubling

Subject: Re: [stella] Cosmic Ark scanline pixel doubling
From: Adam Wozniak <adam@xxxxxxxxxxxxxxxx>
Date: Tue, 15 Mar 2005 15:19:57 -0500
Hash: SHA1

On Sat, 12 Mar 2005, Eckhard Stolberg wrote:
> > I assume you're refering to this post from back in 1997?
> >
> Yes, that's what I'm referring too. Although I later found out
> that the shift actually is 17 pixels to the left in each scanline.
> Also the "missing" pixel always happens in the scanline that comes
> after a scanline where the missile was displayed over the first
> pixel of a playfield block.

Oi vey, did you get me started.  I still don't have it figured out though.

I assume you've seen this:

It seems that Brad was pretty thorough, at least with the P0/P1 moves.
He doesn't mention any 17 pixel moves though.  Perhaps this chart is
different for M0/M1/BL ?  Someone should perform the experiment.

What baffles me is that you're seeing a difference based on which SCANLINE
you're in.  I don't think there's anyplace inside the TIA which actually
counts scanlines, or does anything different based on anything like that
(with the possible exception of the VDEL values, which I don't think is
an issue here).  76*3 = 228, so clk and phi0 should have the same phase
orientation at the beginning of each scanline.

- -- 

"Feminist?  Why would I want to alienate half the population?  I'm an egalitarian."

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