On Mon, 2007-06-11 at 11:14 -0700, Ian Romanick wrote: > The problem is that a few of the GLX extensions (e.g., > GLX_SGI_video_sync and GLX_OML_sync_control) allow applications to query > the vblank counter directly. I don't know of other hardware that > maintains an actual counter. I know that MGA doesn't, and I'm pretty > sure that Via doesn't either.
Radeon and Intel do keep an internal counter. I posted an outline for keeping the counter reasonably smoothly monotonic as seen by applications which should make it work across mode switches too. There is a huge power savings advantage to using the chip-resident counters as we don't have to wake up the CPU every frame to bump a counter. For chips which do not provide a counter, the driver is welcome to synthesize one in software. I was thinking that this could even be done by estimating based on wall clock time, which should be sufficient in most cases by enabling interrupts periodically to resync to the frame counter edge. Going from 16ms wakeups to 2000ms wakeups is a huge potential power savings. -- [EMAIL PROTECTED]
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