----- Original Message -----
From: Peter Pachla <peter.pachla@xxxxxxxxxxxxxxxxx>
To: <stella@xxxxxxxxxxx>
Sent: Tuesday, April 25, 2000 4:58 PM
Subject: Re: [stella] Hardware comparisons
> Hi Kurt,
>
> > Does anyone know more about that display list? Which things can
> >the ANTIC change in each scanline without CPU interaction?
>
> OK ANTIC *IS* a CPU, albeit one with a very simple instruction set,
> dedicated to generating the display (with help from C/GTIA). The display
> list is the program which tells ANTIC how to generate the display.
Actually ANTIC is a coprocessor. A system can only have one *central*
processing unit, after all.
> AFAIR, without intervention from the 6502, all ANTIC can change on a
> scanline by scanline basis is the display mode.
ANTIC can also change where display data is being fetched from, where
display list data is fetched from, and insert blank lines.
> Once you've reached the maximum fine scroll value (depends on display
mode)
> you update the LMS instructions in the display list (these tell ANTIC from
> where in RAM to fetch display data) so that data is fetched from a new
part
> of RAM, your "hard scroll"....this means you don't have to shift any of
your
> screen data around.
You mean "coarse scroll". A hard scroll is in fact physically moving display
data around.
--
Clay Halliwell | ATARI XL/XE DO + THE
clay.FAKEMEAT.h@xxxxxxx | 8 - B I T S --------
e.halliwell@xxxxxxxxx | /////////// M A T H
Keeper of the Atari Jaguar Cheats and Codes FAQ. Request your copy today!
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http://www.atarihq.com/jeo/ "Where do you want to play Atari today?"
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