I recently upgraded my PC and now had a lot of components left over and decided to build a second semi-gaming capable PC.
CPU: Core2Quad Q9550
GPU: Radeon HD 5770
RAM: 2x2GB DDR2
Motherboard: Asus P5QLD PRO
PSU: be quiet! Pure Power 530W
At first I booted from an old harddrive with Ubuntu already installed. It worked fine until I started XBMC. Whenever the scrolling text at the bottom moved it made weird noises (out of the actual speakers, not onboard or transistors) and the text slowed down and sped up every second or so together with a change in noise. When watching a show it didn't cause any problems as long as only the video was onscreen, but as soon as I paused and the pause menu appeared it made that noise again. After a few minutes in that state it would also produce weird graphics artifacts. I assumed it was a problem with my old Ubuntu install and I got a second harddrive and installed Windows 7 on it. As soon as I had installed the graphics drivers it made the same weird noise anytime the GPU rendered a frame. The higher the framerate the higher pitched the noise became. Scrolling Chrome produced a high pitched noise while some complex pixel shaders with a very low framerate caused only a little beep with every frame. I assumed it might be the PSU (I had my old 700W PSU in there which had already caused problems in my new build) and used the be quiet! instead since 530W should be plenty for a 5770 anyways. I booted both OSs again and had exactly the same problems in both of them. I assumed it might be the mainboard (I used my old P5B SE at first) and used the newer P5QLD PRO instead. The same problems continued exactly as before in both OSs.
At this point I thought only the GPU could cause problems like that. So I took the 5770 and replaced the 5870 in my (half) new build with it and everything worked without any problems at all. So the GPU can't be broken either.
So in summary:
It's not the mainboard.
It's not the GPU.
It's not the PSU.
What's left is:
The harddrives (not really since I used two different ones for the two OSs)
The TV I connected the PC to
From my knowledge none of them could produce audio and graphics artifacts like what I'm seeing. Any ideas?
I do still have 4x1GB DDR2 RAM, a Q6600, a few old 80GB harddrives and another TV if you think replacing any of these parts is even worth a try.
I did a little more experimenting and it appears the graphics artifacts and the sound problems are separate problems. Since I only experienced the graphics artifacts in Linux I tried playing Saints Row IV on Windows and while it made the weird noise it run without any graphics or performance problems.
I didn't find out much about the origin of the noise, but I still learned a bit about it. If I mute my TV (where the AUX cable is plugged in; I'm using VGA for video since my TV supports that natively) the noise is gone, if I mute the PC in Windows the noise stays. Moving the cable around changes exactly nothing, so it's not interference. The noise happens exactly when a frame is rendered. I can even hear changes in framerate. Maybe it doesn't even have anything to do with GPU usage, and it always happens when a frame was rendered (not while it is being rendered though). I don't know enough about graphics to understand why this is only happening in games and glsl.heroku.com, but not when using Windows normally.