Davey wrote...
Hi,
I'm not real familiar with the
Atari
computers, even though I now own 3,
a 600XL, 800XL and a 130XE. I
read that
the Atari computers had 3
custom chips for graphics and
sound called
GTIA, Pokey and Antic. Can
anyone tell me please exactly
what aspects
each chip controlled and what
the changes were in each during
the
successive revisions from the
original to the XL to the XE? I
can find
no detailed explanation thus far.

GTIA handled converting the graphics and text
information into RGB video data for combining
to make
rf and video. I think it is also responsible
for
fetching Player/missle data for overlay and in
collision detection. It supports 16
color/luminance
modes the older CTIA did not have.

Antic is responsible for creating the screen
from the
display list instructions and pointing to the
right
data. It updates memory so GTIA knows what
mode line
is being used. A later version added an
extra bit for accessing
memory past 64K, for ram upgrades.

Pokey is responsible for audio..sound
channels, tape
i/o noise, timer functions, and the keyboard
scanning.

There are references..Computes Mapping the
Atari, de re
Atari, and a FAQ by Michael Current.

Rick D.

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