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Old 01-25-07, 04:02 PM   #13
nagini
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Default Re: VSYNC Problems 9xxx drivers (Framelock trouble)

OK, gotcha, I will have to go to the data center here and disconnect the cables.

This image is from the center (master) without any framelock turned on- or configured even.

http://www.ust.ucla.edu/~friedman/pu...ter-sgd-30.png

----

I will post again once the cables are disconnected in about 15 min.
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Old 01-25-07, 04:11 PM   #14
nagini
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Default Re: VSYNC Problems 9xxx drivers (Framelock trouble)

OK, G-Sync cables disconnected. Cleared framelock config in nvidia-settings and ran swap-group-demo -g -b

Here is a screen shot

http://www.ust.ucla.edu/~friedman/pu...sconnected.png

Still 30fps.

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I found another G-Sync card and I am going to put it into another identical system I have here. It is not connected to any other systems and has the same FX4500's in it. I think the only difference is that it's a single core system - all the others are dual core.
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Old 01-25-07, 04:22 PM   #15
nagini
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Default Re: VSYNC Problems 9xxx drivers (Framelock trouble)

Eureka! I think we have narrowed things down here. The problem has something to do with enabling the stereo. we usually set the stereo to active "3" on the boards. I removed those from xorg.conf and restarted X. confirmed the stereo visuals were gone and then ran again. Bang swap_group_demo runs at 60fps. Interestingly, when I put the stereo back it still works at 60fps. If, however, I kill X, rmmod nvidia, modprobe nvidia, enable stereo it goes back to 30fps.

I can provide images if you like.

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Actually, we set up another system and can confirm this. Without the stereo set everything runs faster. If stereo is enabled when the module is loaded things go bad. Is there some way you can confirm this too, or not?

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More detail - it appears that it is not specifically related to "Stereo" but to "ForceStereoFlipping".

Last edited by nagini; 01-25-07 at 04:40 PM.
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Old 01-25-07, 04:46 PM   #16
nagini
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Default Re: VSYNC Problems 9xxx drivers (Framelock trouble)

Definitely, "ForceStereoFlipping" "true" causes the problem we have been looking at here. reproduced on two systems. I am not sure what it does anyway - have to ask the system administrators why it is in there - can you enlighten me as to why one would use it?

Anyway...

"Stereo" "3"
"ForceStereoFlipping" "true"

Causes the problem and generally hoses performance

"Stereo" "3"

or, no stereo at all does not show the symptoms.
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Old 01-26-07, 10:56 AM   #17
netllama
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Default Re: VSYNC Problems 9xxx drivers (Framelock trouble)

The ForceStereoFlipping option instructs the driver to ensure/force stereo flipping even when no stereo drawables are visible. Generally speaking, using active Stereo means that each 'eye' of the stereo glasses updates for each VBLANK. As a result, the application requires two VBLANKs to completely refresh, which is why you're getting a FPS rate that is half your VBLANK.
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Old 01-26-07, 01:53 PM   #18
nagini
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Default Re: VSYNC Problems 9xxx drivers (Framelock trouble)

I see, I found the description in the documentation too. I asked the system administrators about why they put it in there and they told me they thought it's function was similar to the flipping setting for opengl, but for stereo. Clearly it is not. I don't know, the description made sense to me when I read it! Anyway, this explains all kinds of things for us.

Thanks for your time.
Scott
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Old 01-27-07, 11:22 AM   #19
squeen
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Default Re: VSYNC Problems 9xxx drivers (Framelock trouble)

Nothing comes for free. Stereo = 2 draws, one per eye channel = 1/2 frame rate.

I'm been looking at some ways to chain systems together with frame grabbers boards (DMA to host memory). In other words, two SLI systems in SFR rendering output a single eye channel on the DVI connector. Framegrabber boards in a third workstation take the two channels into textures via PBO's and then that system's graphics board does fast draws of screen aligned quads in a stereo output mode. All this work just to keep the frame rate up when steroeo is active. It remains to been seen what the latencies implied will do.
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