Re: Apple II vs Atari 800

[heuser.marcus@freenet.de]

On Apr 21, 8:56 am, "Russg" <russg...@MUNGEsbcglobal.net> wrote:
>
> Seems like the C=64 has a fixed screen memory,
> and you're poking into that memory.

You can set the frame buffer of the C64 to various locations.
Page flipping is possible, of course.

> That can be done on the Atari.  The Atari screen
> memory can be moved, as can the display list,
> which is a small program for the graphics chip
> to execute.

That's right - and funny things are possible with these display
lists: The start of the frame buffer can be set for each line -
organizing the frame buffer "backwards" in memory, a different
video mode for each line, a horizontal display interrupt on each
line (if one can spare the CPU cycles ;-) and so on.
It's apparently even possible to change the video mode mid-line!

The power of ANTIC (the video processor) was astonishing for
its time.

But the C64 has one single feature that is much more practical
for many applications:
The 1KB large "Color RAM" area which allows for two independent
colors for each character block (40x25 matrix) - even in high
res mode.
This not only gives you colored text but a good compromise
between colors and resolution whereas the Atari either can't
utilize that many colors on a single line or has a lower resolution.

bye
Marcus