Random frame rate drop with SteamVR

We’ve been using SteamVR in 2 projects recently and have found that in both of them sometimes the game will suddenly drop to under 10FPS (from 100+), stay there for a few seconds and then freeze Unity so that we have to end task to quit. Most of the time the games run just fine when we enter play mode, it just seems random as restarting Unity and running the game again will fix the issue and it will work again for the next few hours.

This is on a Windows pc, so I’m not sure if it could be tied to something that windows is doing every once in a while? I’m not running any sort of virus scanning software or anything like that that I know of, but if anyone has experienced this or has any thoughts on what to test it would be greatly appreciated.

Sounds like it might be your CPU or GPU throttling due to heat, you can try monitoring the temperature and clock speed with a program like GPUZ.

Maybe, that’s a possibility. The only weird thing is that it’s never happened in any of the actual VR games I’ve been running, even after long play sessions where the computer has heated up a lot. But I’ve just updated to 5.4 beta and so far haven’t seen this happen again (along with a nice performance boost in my game).

Update. It’s still happening with 5.4b16, it’s definitely not heat related as I’ve checked the temp and it happens at regular temps of 50C CPU and 40C System. It does seem more related to the vive itself or the steamVR connection. Last time it was happening I had trouble getting the vive HMD to work in SteamVR (from the steam app) until I turned off direct mode, then rebooted the HMD and then changed back to direct mode. So maybe something is going wrong with the direct mode or my particular video card, and resetting that mode fixes it. To note, rebooting the computer or just rebooting the vive without switching direct mode on/off does not fix the issue.

I experienced this problem too. My cpu occasionally cuts the clock rate in half (for example 2.0 Ghz becomes 1.0Ghz) suddenly. Of course the program stutters when this happens.

This problem is occurring especially in the Unity3d Editor after a while of running it in VR mode with the vive.
Also in “The Lab” Demo this error appears.

All other programs are clocking fine on the CPU.

BUT I found a quick fix for this. I disabled the C- State settings in my BIOS, after that the CPU was constantly running at the same speed. Unfortunately the CPU wastes a lot of energy this way, because all core are clocked at maximum all the time. So this is not a real fix in my opinion.

I can not confirm yet that is only occurs with Unity, but there might be a connection.