Hi! > > We may have confusion here. > > > > On PC, it is definitely not possible to enter sleep state > > between frames of video... because video is powered off. > > > > On PC, sleep states are *system* sleep states. CPU sleep > > states exist, too, but that's in-kernel implementation > > detail. They are called C1..C4. > --- > > Well, we have some hardware where we can sleep everything but > memory and some where we can also leave the display active (and > backlit). In fact, however, today the latency for going to sleep > is too great to do so between frames, so we just do a wait there. > We would LIKE to be able to sleep there at some point in the > future and would prefer a power model that made that cleanly > part of a continuum of operating points. > > However, we definitely DO sleep (with self-refreshing RAM) during > relatively short periods, with the wakeup resulting from an > interrupt from the RTC (which is self-powered and is set > to timeout at the next scheduled timer when we go to sleep) > or another hardware interrupt. We think of this as a system-level > sleep state. > > I'm not sure how you distinguish between a "system" sleep state > and a "CPU" sleep state - seems like there's a collection of > things that can be shut down or not; except for true OFF, there's > always something on. Well, even in "true OFF", RTC keeps ticking. And in "disk" state (swsusp), machine is basically "true OFF" but it still retains state. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
