[BUG] Nvidia driver forcing CPU into a low power state when UE4/UE3 is focused

Specs: Win64 8.1 i7 4700HQ@3.2Ghz, GT 750M (344.75) 4GB, 16GB ram, SSD, clean installation (Laptop)

As soon as you click on UE4 (4.5.1, 4.6) window the CPU freq jumps from 3.2GHz to 0.77GHz.
This is not caused by overheating.
Scene is empty, CPU is idle and only Cpu-Z and windows Task Manager are ruuning.
Windows power management is set to 100% for both minimum and maximum state.

This ONLY happens with UE4.
However I’ve noticed Thief(2014) which uses UDK (afaik) having the same issue.
Unity for example does not have this problem on the same machine.

It seems the Nvidia driver is changing the CPU power management policy resulting in an immediate underclocking.
On #unrealengine somebody mentioned “the engine may have some weird API call combo which triggers a buggy code path in the driver”.

This bug forces Unreal to have a FPS < 50Hz on an minimal scene.

Thank you.

(Note the OS and CPU-z reads CPU max freq at 2.4 but it is 3.2 actually)

Hey maverick1999,

Are you using the newest Nvidia drivers? If this issue is caused by the Nvidia driver, then going to another version (newer or older) could be a temporary solution until we can find the root of the problem.

Hi maverick1999,

We haven’t heard from you in a while, so we’re marking this post as Resolved for tracking purposes. If you’re still having trouble with this issue, please respond and we’ll resume work on it.

Thanks,

Jonathan