What happens to LCD if refresh rate is set too high?

[tbuht_1]

I was wondering if there are any negative effects to your monitor/LCD if you set the refresh rate past the monitor's capability? My system is a dell inspiron 1520 and it said the refresh rate was 60 hZ when I was using Vista but when I switched to Ubuntu and checked Compiz, my refresh rate was set at 50. I changed it to 60, but noticed that there is a slider that allows you to increase it way higher. I'm just afraid to do this so I was wondering what are the effects if set too high? Also how much higher can I increase it by after 60?

[Deciare]

Your monitor can't display images any faster than it can physically refresh, so setting your refresh rate to something higher than what's supported by your monitor may have the same effect as setting it to something lower than what's supported by your monitor: visible tearing of moving objects. Unless Sync to VBlank is enabled, in which case the frame rate will always be a multiple of 60.

Some people have claimed that setting the refresh rate to 120 or a higher multiple of 60 can improve perceived smoothness even when Sync to VBlank is on.

I don't know whether it would affect the lifespan of your monitor, though.

[azathothgr]

The refresh rate setting in compizconfig manager is actually compiz's target framerate. It does not affect your screen at all. It's there so you can match it to your screen refresh rate, and avoid tearing. If you don't care about tearing, its safe to set it to whatever you like/whatever performs best.
To set your screen refresh rate you should use a different utility, either something like nvidia-settings, or your distribution's screen manager. From there you will not be able to set it higher than what your screen supports, so it should be safe. (On gutsy though, sometimes the default screen and graphics config utility labels the available rates wrongly, so for instance 50hz is actually 60hz, and 54hz is 75. Both correct, just weirdly labeled.)
On a sidenote, afaik, an lcd connected to a digital output will always be at 60hz; the screen app should not let you set it higher. On an analog output, some models support 75 hz too, but change it internally at 60 hz anyways. On the off-chance the screen config utility reports more rates (which, given that you've set your screen as an LCD, should never happen), it's best to leave it at either 60 or 75 if you're not sure. I have absolutely no idea what would happen with a higher refresh rate, but my guess is the monitor will have safeguards for such a thing.
For CRT displays it's usually a case of try and see, as unless your monitor is very old it should just black out if it receives an unsupported refresh rate, and return to the old one, once your config utility's timer runs out (the "click here in 15 secs if you see this" thingy), without damaging the monitor.

[some-guy]

actually, I'm on nvidia and to remove the tearing of windows in wobbly and other effects, I have Detect Refresh Rate as Disabled, and brought mine to 120, any further makes it worse, and I also have Sync2VBlank Enabled or compiz uses way too many resources
:D

Of course for you the amount that you change it won't likely be the same ;)

[tbuht_1]

Very interersting because I have Nvidia Settings as well and I have sync to V-blank on and in compiz I have it off because if I turn it on in compiz, it makes everything jittery, such as when I try to move a window or flip to next workspace, etc... In CCSM, I have detect refresh rate on (should this be on though) and it set my refresh rate at 50 initially, but I changed it to 60. My Nvidia settings tells me my refresh rate is 60 hZ. So the only thing I'm now confused about is whether in CCSM i should set the refresh rate at 54 hZ (according to azathothgr's claim) or should I leave it at something else?
Thanks for the replies!

[Deciare]

Detect Refresh Rate should be disabled in ccsm. The reason Compiz detects the wrong refresh rate is because it retrieves that information from the XRandR extension, which the nvidia driver misuses in a way that nVidia's README (http://us.download.nvidia.com/XFree86/Linux-x86_64/169.07/README/chapter-13.html) does a better job of explaining than I can.

You can make Compiz detect the correct refresh rate by adding this line to your /etc/X11/xorg.conf file:
Option "DynamicTwinView" "false"

But doing so will disable some parts of the nvidia-settings application. Whether you leave it enabled depends on which problem would bother you more, I guess.

[tbuht_1]

Should I add this under the "Screen" section or under the "Monitor" section or just at the end of the file? Thanks 4 the reply.

[azathothgr]

So the only thing I'm now confused about is whether in CCSM i should set the refresh rate at 54 hZ (according to azathothgr's claim) or should I leave it at something else?
Thanks for the replies!

No you misunderstood. 54hz was only a weird label in Ubuntu Gutsy 's Screen config utility. I mentioned it to point that nvidia-settings shows the correct screen refresh rate.
In CCSM you should set compiz' refresh rate (lets call it framerate) to your screen's refresh rate (as seen in nvidia-settings), or a multiple of it. (if your screen is at 60hz, set compiz' framerate at 60 or 120, whatever works best) .
Detect refresh rate should be off, and sync to vblank on.
Once again, the setting in CCSM is not affecting your screen at any way.

[tbuht_1]

Gotcha. Sorry for the misunderstanding. The only problem is that sync to vBlank has to be off under CCSM because if I leave it on everything becomes really jittery, so it is only on under Nvidia settings.
And Deciare, I got your command to work after adding it in xorg.conf because I checked refresh rate under System -> Preferences -> Screen Resolution. It changed to 60 when it was previously 50 hZ.
Thanks

[azathothgr]

It is possible the sync to vblank for opengl, from nvidia settings isn't required .. I know the one under XServer XVideo Settings is better off, when running compiz, but I'm not sure about the setting under OpenGL Settings.. I suppose it's better to only have vsync either in nvidia settings, or in ccsm , not both, but that's a guess. I think that, ideally, if you set your framerate to match your screen refresh rate, you wouldn't see any tearing even without vsync.
Oh, btw, you could use the benchmark plugin to see what exactly is happening with the framerate in compiz.

[SmSpillaz]

If you set the refresh rate within X to something higher than your LCD can handle, your panel will either switch off or display a message stating that the refresh rate has been set too high and is unsupported. Just in case you wanted to know if you did so within X.