John Woodhouse posted on Sat, 30 Apr 2011 08:39:48 -0700 as excerpted:
> On problems in this direction maybe with either driver I did see
> something on the web somewhere relating to "noflip" causing problems one
> way or the other. No interest at the time so no further info.
Yes. The nvidia option is apparently noflip, but on native drivers it's
normally 'Option "EnablePageFlip" "boolean"' (where boolean can be
yes/true/1 or no/false/0).
Page flipping is where, instead of the driver having a page back-buffer
and front-buffer, composing stuff in the back-buffer then blitting (fast-
block-copying) it over to the front-buffer, when the image in the back-
buffer is finished being composed, the pointers for the front- and back-
buffers will reverse, so the former back-buffer is now the front-buffer
that's direct-painted to screen, while the former front-buffer is now the
back-buffer, where the next screen image is composed.
Because page-flipping only involves two memory address pointers instead of
blitting the whole area that has changed, it's **FAR** faster and much
more optimized than the blitting method. Done well, it avoids tearing and
certain other artifacts too, by timing things so the page flip only
happens when nothing drawing into the buffer.
But that's the challenge, getting and keeping everything in sync. If the
page flips at the wrong time, bad things can happen, ugly artifacts, even
crashes, and graphics crashes are definitely capable of taking the whole
kernel and thus the entire system with them.
The the option.
And yes, I've definitely read that turning no-flip on can help
dramatically with specific nVidia hardware and drivers.
--
Duncan - List replies preferred. No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master." Richard Stallman
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