Polling loop good here???
- From: Frank Kotler <fbkotler@xxxxxxxxxxx>
- Date: Sat, 27 Aug 2005 20:32:55 -0400
At the risk of beating a dead horse... This question just popped up on the linux-assembly list. Hasn't gotten any answers yet, and I don't know a good answer...
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Any ideas how I might sync to bit 3 of port 0x3DA, the video card's vertical sync signal?
Just watching the bit in a loop doesn't seem like a good idea, since the CPU could be off doing something else, but as far as I know any timer function I might use will only be accurate to 1/100 of a second, which wouldn't be much better than watching the bit in a loop.
Since things like DOOM run in Linux, I think there must be some way to do it. I've discovered that simutaneously changing the screen data and the color palette without synchronization creates a flicker of a mess on the screen, and DOOM doesn't do that in Linux, so I guess it must be synchronizing somehow.
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I suspect we're all agreed (?) that it would be really cool if there were an interrupt on vertical retrace, but there isn't. There may be a way to "block" waiting for this, but I don't know how to do it. I fear we may be "stuck with" a polling loop here...
Anybody know the "right" way to do this?
Best, Frank
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