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Don Luca

[HowTo] Permanently disable BeamSync

27 posts in this topic

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I've done a bit of digging and I have found someone giving this explanation


The "beam sync" you are referring to is the new "Automatic Beam Synchronization" feature of Tiger. This is equivalent to enabling "vertical refresh" on some games if you have a CRT monitor. The idea is your monitor, if it is a CRT, can only display one frame of video per cycle of the electron gun (or "beam") that is blasting the image on to the back of the screen.


The gun starts at the top, moves to the bottom, and then, without "drawing" anything, moves back to the top to start over again. This period where it moves back to the top is called the "vertical refresh". If you can sync all of your drawing routines to that vertical refresh period, then the monitor will display a new frame every cycle of its beam, and your video will be as smooth as is physically possible.


That is what Tiger's "beam sync" aims to do: to take the "vertical refresh" feature of high-performance 3d games and make it an operating-system level feature.


Unfortunately, the implementation seems a little wonky. Depending on how fast your computer is (if it's not fast enough, you may not be able to fit everything into a single retrace and have to wait longer than normal for the next one to come around), and wether you have an LCD or CRT monitor (LCDs don't have a vertical retrace -- there's no "beam" in them), and, apparently, a whole lot of other stuff, auto beam sync may actually slow performance.


There's an interesting thread at the dev list about this:



In the mean time, the story is pretty much the same as Q2DX. Test it through trial and error and see which one gives you smoother results. When 10.4.2 comes out, test it again in case Apple has fixed it.


One other note: be sure to test how it LOOKS and not how many FPS you get. Syncing, by it's nature, limits your FPS to the refresh rate of your monitor. An FPS that is greater than your monitors refresh can actually produce choppier results, so limiting FPS is sometimes a good thing ;-)


Not sure what to think, but he seems to know what he's on about!

Found it on this page

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I'm sorry but why on earth would anyone want to disable Beam Sync (aka vsync)?!! This will break the harmony of monitor refresh and graphics refresh timings, and will introduce horribly ugly tearing when moving windows, playing games and watching movies.


There was an old buggy version of Xbench, which apparently did not turn vsync temporarily off while doing measurements, so people got higher results by manually disabling it. But of course this will not make your computer any bit faster in reality (we have no use for FPS which is more than the refresh rate of out monitors).

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