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Subject: Re: Re[2]: Grayscale Display/ Picture Viewer/ HDD Upgrade
From: DillonCo_at_attbi.com
Date: 2003-01-02


> In the end of the game SOKOBAN, if you pass the 101st level (or just
> keep on hitting F3) then it flashes the entire screen. I think it is
> EASILY quick enough for grayscale. You could have a 3 color grayscale
> with just two different bitmaps.

The point is, although it is feasible to make crappy grayscale, it would
probably end up being very flickery and consume most of the processor time.
Just looking at what needs to be done:

120x70 bits (screen size)
About 2 instructions overhead for each byte
About 6 instructions are executed for each bit

Multiply that out and there are 52500 instructions to update the screen.
The average instruction will take, say 4 clocks, so that 210000 clocks.
Finally, each byte need to be read adding a decent amount of clocks (I don't
know how many, so I'll ignore this). Divide the processor speed by thins,
and you'll find that the screen will update about 50 times a second using
full processor time. That won't work.



Page was last modified "Jan 10 2012" The Rockbox Crew
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