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Re: [OT] Video games (Was Re: [vox] silicon valley computer stores)
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Re: [OT] Video games (Was Re: [vox] silicon valley computer stores)

On Sat, Oct 18, 2003 at 12:26:00AM -0700, John C. Alden wrote:
> But hey, a monochrome CRT + a few gels and some tape

I always wondered if this 'cheat' was what inspired Jay Miner to create
the Display List Interrupt system on the Atari 8-bit (and later
the similar Copper system on the Amiga).

At any point down the vertical resolution of the screen (e.g., 24 times
in text mode, 12 times in 'big text' mode, and up to 192 times or more
in the various pixel graphics modes)... or if you timed it right, anywhere
WITHIN these spots (so therefore pretty much any of the 200+ scanlines
on the display), you can interrupt the graphics chip, jump back over to the
CPU for a moment, and from there do tricks like change the color palette
(think colored gels taped to the screen ;^) ), reposition the 'sprites'[*],
or change the horizontal fine scroll register.

[*] Known as "Player/Missile Graphics" on the Atari.
    Last weekend, I learned they're called "Motion Objects" in the
    arcade biz. :^)
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