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GarethC

OpenGL Graphics code causing electrical noise

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Hi all, I'm having a pretty strange issue here, hopefully somebody could please give me some insight to possible sources of the problem. It's also a hardware glitch (possibly), so I wasn't too sure where to put this. OpenGL made the most sense as that is the graphics API I am using. I have some code that uses OpenGL to render height-fields/terrains. I recently attempted to improve upon it by adding geo-mipmapping. The addition was a success and notable performance increases were achieved. However, I noticed that my video-card was making electrical noise while I was running my demo. For those unfamiliar with this event, the circuitry of the card makes very high pitched squealing noises. Usually electrical noise is indicative of a hardware problem (I have this card under an extended warranty thank goodness!), but this case was a bit different. Allow me to explain. When I am rendering the terrain at maximum quality, either the noise is not present or it is too high-pitched for me to hear. When I lower the overall quality of the terrain, I begin to hear the sound. Strangely enough, it becomes easier to make out with every consecutive shrink in the number of triangles being rendered. Less stress = more noise? This didn't make sense to me. I tested out the card with various DirectX and OpenGL titles including Crysis, Battlefield 2 and QW - Enemy Territory. Nothing. Zip. Nada. All quiet. It seems that it's only my code that causes this. This worries me. In short, what I am asking is, has anybody else had or heard of this issue? What could it be indicative of? I have only one hypothesis to date. I am rendering the terrain with VBOs and the indice sets are stored in one large buffer. As I decrease quality, the indices are pulled from memory higher and higher up from the start of the buffer. This could mean I'm moving from one memory chip to another (couldn't it?), which might mean one of the chips is the little whiner. But why do other games operate fine then? Any help/ideas/insight would be greatly appreciated, I can paste code as necessary. (There's really nothing out of the ordinary about it though...) If it's not likely to be my code or a software issue then I'll just get the card replaced and try again. Many thanks! :) By the way, the card is an 8800GT (512mb) operating with the latest drivers (updated them yesterday, although the problem existed before the update.) EDIT: It occurred to me to test the code on another card (8600 GTS). Silly of me not to think of this sooner. In any case, it doesn't do it on that card. This reduces the odds that it's a software issue, I suppose.

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I've had the same thing occur, goes away when I v-sync (that or actually fire enough work at my GPU so it isn't going at 1500fps+).

Regards,
ViLiO

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also stick a pause in your main loop eg 5 msec's so the CPU is not working overtime for nothing

about the problem, it could be the fan (thats one of the first things to go), easily tested by when the machines going + making the noise, stick your finger in lightly apply presure to the top of the fan.

, in past days u could just tighten the screws aka fix it yourself, but nowadays manufacturers are not to happy about this, (due to you less likely to buy a new part if u fix the broken one) thus have made hardware thats more difficult/impossible to repair

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Quote:
Original post by GarethC
Usually electrical noise is indicative of a hardware problem (I have this card under an extended warranty thank goodness!), but this case was a bit different. Allow me to explain. When I am rendering the terrain at maximum quality, either the noise is not present or it is too high-pitched for me to hear. When I lower the overall quality of the terrain, I begin to hear the sound. Strangely enough, it becomes easier to make out with every consecutive shrink in the number of triangles being rendered. Less stress = more noise? This didn't make sense to me.

Let me begin by saying I experience the exact same symptomps as you with my GeForce 8800GTX 768MB.

I think it's very likely you're seeing the same thing as I am. But it seems like you're misunderstanding the source of the problem. It's not the workload that causes the high-pitched noise, but rather 'high FPS'.

It seems like this card emits that noise whenever it's allowed to render at extremely high rates (1000 fps or higher). I've noticed this happen with my own OpenGL applications, and with many other old games I've tried.

The only solution, it seems, is to limit the frame-rate by using V-Sync. Don't let it run at 1000+ Fps. I'm not sure if it's a big problem, i.e. if it damages the card or not, but I prefer not to try it just in case.

If I had to guess, it's probably some sort of a common nVidia problem affecting some 8xxx series cards and maybe others. I've never gotten this before with my past ATI vide cards - but then again, I've never gotten 1000+ fps with them either. [smile]

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Probably the power regulator circuits. The high power consumption of GPUs usually require swithing power regulators, that operate at a high oscillation frequency. Under certain varying loads, interferences can occur, and you can hear these through vibrations of the capacitors and/or coils.

If its not so loud to be annoying, this is not really a problem.

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Oh wow, this explains quite a bit. While at the highest LOD the card manages 500 FPS (without extra scene details), but when I turn the LOD down it does to 1500 then as high as 5000. I had V-sync turned off to test the performance gains (otherwise it clamps out at 60fps).

I'll half to try fixing my draw/update timers so this doesn't happen again.

Geeze, I was about to go out and replace it just this moment. Good thing I checked here first. Thanks for all your help guys/gals, it's much appreciated!

:)

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