Re: Flyback

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From: Chris Atenasio (chris@crud.net)
Date: Thu 13 Jan 2000 - 04:42:49 IST


> > vga_waitretrace() does indeed seem to do what I want.I've read the man
> > page, but it does not state whether the function returns when the beam
> > gets to the bottom right of the screen, or if it returns after it
> > returns to the top left of the screen to begin retracing.Does anyone
> > know?
> 
> It seems to me that the function returns at the end of the retrace.

Would it make sense then to keep an internal timer, calibrated with
vga_waitretrace(), and sync draws to that?  Lets see, 200,000 hz cpu /
70 hz refresh gives ~2857 cpu cycles between refreshes.  Take into
account that the retrace is a fraction of the refresh time, and you
are dealing with somewhere < 2857 cycles, which is fine for something
simple, but wont give you time to blit images.  Then again I may be
calculating something wrong... 

shrug :)

- Chris
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