>
> Writting a programme to draw horizontal colour bars would be a piece of cake.
> But vertical bars is a bit more difficult because you have to change the
> the playfield graphics registers in mid scan line.
>
> Does anyone know what the pixels:cycles ratio for playfield graphics is?
> Could you time it to change the graphic's colour register in mid-pixel to
> get a higher resolution, or would it not accept the change until it finishes
> the current pixel?
The ratio of pixels to CPU cycles is 3:1 exactly. The fastest you could
change colors is in 9 pixel increments:
STA COLUMPF ; 3 cycles x 3 pixels per = 9 cycles
STX COLUMPF
STY COLUMPF
But then you run out of registers and need time to reload. You can get
extra mileage out of storing to COLUMBK and matching the timing against
what's in the playfield data, and probably get single pixel colors, but
not consistently across much of the screen.
I don't see a way to get 16 even-width bars on one scanline. Eight should
be doable, with 16 rows of bars to encompass the whole colormap.
- Jim
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