Glenn Saunders wrote:
> I think the sprites on the C=64 were also at 320 pixel resolution, vs. the
> 160 resolution on the Atari.
Yes.
> But the color really bugs me. Only 16 shades on the C= tend towards games
> that are really posterized and unbalanced, aesthetically, whereas you can
> be more creative and artistic in picking colors on the Atari.
But the ability to have those colours freely usable on the same
horizontal line more often than not made up for the smaller
palette.
> also supports hardware scrolling of the background. Not sure about the
> C=64. The C=64's graphics memory map was kinda weird. The Atari stores
The C=64 allowed you to scroll from 0-7 pixels horizontally and
vertically - then it was up to the program to shift all of memory
over one character. As long as you weren't trying to scroll a
full bitmap (8k of data) you could get a very smooth scroll -
60 fps on an NTSC machine.
> graphics memory in a more conventional chunky pixel format. The options in
> drawing to the screen with the Atari were numerous because of all of the
> available graphics/text modes. The C=64 didn't have that kind of
> variety. You could have part of the screen be text (for scores) and part
> be a GTIA 16-shade mode, and part a 160x200/4 color mode, and so on. There
> are all sorts of interesting effects that can be achieved through display
> lists.
The C=64 also allowed all sorts of split-screen modes - you'd just
change (through the use of interrupt routines) from text/multi-colour
/extended "text" mode (really, 8x8 tiles) to the hires and multi-colour
hires modes.
> The Atari clock is 1/2 NTSC colorburst instead of 1/3rd, so it's still
> closely tied to TV timings, unlike the C=. So it's still possible to do
> 2600-like effects and get through to the hardware while the screen is being
> drawn.
This is totally possible and common on the C64 - 8 pixels are drawn for
every 1 processor clock - on an NTSC machine there are always 65 cycles
per scanline, on PAL, 63. 262 scanlines per NTSC frame, 312 per PAL
frame.
> I haven't played them on the C=64, but games like Archon which rely on
> having 8 shades of gray it can cycle through must look pretty lame on the C=64.
White, black, and three shades of gray :)
> Remember that there is a strip of memory representing the sprite. I think
> the C=64 sprites have a physical length to them much smaller than the
> entire screen. So you can paint more of the screen vertically with Atari
> sprites. You can also reposition a sprite in mid screen similar to the
Yes, a C=64 sprite is 21 pixels tall. However, sprites can be re-used
vertically.
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Robin Harbron macbeth@xxxxxx
http://www.tbaytel.net/macbeth
http://www.psw.nu/
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