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Forums > C64 Coding > Sprites over blanked screen

2005-12-07 23:39

peskanov
Account closed

Registered: Mar 2004
Posts: 17

Sprites over blanked screen

Hi there; I am working on a small effect using sprites. I don't need any kind of backdrop, just the sprites and raster interrupt in the odd lines.
To free cycles I am poking the $d011 register in each IRQ to disable bad lines.

Well, the question is that I have been looking some demos to see the ways used by others coders, and to my surprise I have disassembled a demo which displays the sprites over a blanked screen!?

It's Comajob from Crest. The sprite strech effect works with the 4th bit of $d011 cleared, along all the screen (as far as I have seen).

I am totally puzzled, is there a way to display sprites over a deactivated screen?

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2005-12-11 18:00

Monte Carlos

Registered: Jun 2004
Posts: 359

On the borders you'll always see only black, when in
hires bitmap mode. This doesnt depend on which other
d011 bits are set. So it doesnt depend on having an illegal
or not an illegal mode.
d021 is not read out anymore.

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