Bizarre Noise from GPU - KSP ONLY!

[angelatthetomb]

Here's a weird one....

Trying to run KSP on Linux Mint 17. Specs are GTX 970, i7 4790k 4.0ghz, 16gb RAM. The problem below occurs with three different nVidia-proprietary drivers (the Nouveau drivers don't support the 970).

The first indication of something going wrong is randomly alternating pegged CPUs as soon as KSP starts loading. Watching in a CPU graph first CPU 1 will peg to 100%, then CPU 4, then CPU 7, or whatever, randomly. Seems to switch every three or four seconds. This continues through the loading process and in the game itself (main screen, menus, in flight, everywhere). This comes with pretty poor performance for this machine (random stutters and jitters even with a 3-part craft). It occurs at all graphics settings, with or without mods, x86 or x86_64, whatever. The same machine in Windows never gets CPU pegged from KSP; usually only using 20-25% of one core.

What's scarier though is the sound the GPU starts to make as soon as the main screen loads. It's a high-pitched modulated whine or buzz. It's definitely not the fans; it cuts in and out and it sounds synthesized. It reminds me a little of old 56K modem noises. It's definitely coming from the GPU.

Once I pull the 970 and switch to integrated graphics (and deinstall all the nVidia drivers), everything works great. I can load big ships with no lag at all, load it up with mods, no problems. As soon as I switch back to the 970 the CPU pegging and noise come back.

I've never had problems with the card and never heard this sound anywhere but in KSP (including in Windows or in OS X). Other games run fine in Linux.

Any ideas?

[Peder]

Hmmm if you only have this issue with KSP, then I would say you should try to use an older video driver and see if that help you.

[angelatthetomb]

Thanks for the tip Peder, tried the oldest available Nvidia drivers that support the 970, issue still there.

I've figured out the noise is "coil noise" from the capacitors, which occurs when the GPU is under extreme load. That gave me the idea to check my GPU temps and lo and behold, they're spiked too. GPU usage is at 100%. So is CPU.

Something is making KSP use maximum available resources on a system that shouldn't shrug at it (and performs well under the iGPU at nowhere near maximum loads.) What could do that?

[waterlubber]

I'm sensing that the drivers are at fault...ir Unity. Try installing from Nvidia's site.

[ainurakne]

I always get this whine if VSync / sync to vblank is disabled for whatever 3D application. When there is no limit, the GPU renders frames as fast as it can, hence the extreme load. It can also choke the CPU, which must then execute rendering loop continuously without a break to feed the GPU with the data and rendering commands.

Check KSP VSync or framerate limiting settings under graphics tab.

Hope that helps.

EDIT: I've got Linux Mint 17.1 myself, using GTX 560 Ti with proprietary drivers.

I recall that when 0.90 came out, I had some problems, because those settings didn't work as they used to anymore. In the end I settled with VSync turned off and framerate limiter set to 60 FPS. That did the trick for me.

Edited April 17, 2015 by ainurakne
Additional information

[tschieggm]

Check KSP VSync or framerate limiting settings under graphics tab.

Thanks for the solution!

I ran into this problem today on Ubuntu with a GTX 970 and tweaking the VSync settings made the noise go away.