low FPS when alt+tabbing? cant figure out whats causing this?

hi gang. PLEASE tell me someone here can help me with my UDK 4 problem. Once i upgraded to 4.11 udk boots up, its running my scene at 120 fps, i can go look at chrome for a while, come back and (completeley random it seems) udk is running at 11fps. so i’ve tried closing spotify for example, BOOM, udk is running at 120 fps again…ok i thought, i fixed it, udk doesn’t like spotify? but…its random, my fps will eventually go back down to 11fps if i alt tab off udk? this has been plaguing me a few weeks now. its SO random and i cant figure out whats causing this.

here are my specs. udk was working fine i thought until 4.11 came out. this is killing me not having fast fps all the time. it makes no sense. i’ve disabled windows firewall and that made no difference, i cant figure out…meh!!! please help.


win 10
32bg ram
intel i-7
nvidia geforce gtx660

Something running in the background may be interfering.

I’ve been seeing the same or similar problem in 4.10 for months…
But I dismissed it because of other Asus ROG GPU problems.
Now after reading your post, it makes me wonder again…

UE4 has an idle editor setting when running as a background window…
Does UE4 ever get stuck in this low priority mode after alt-tabbing back?
Its like critical-power / low-battery mode switching not background apps.

its…incredibly frustrating to say the least…

a workaround is to disable “use less CPU when in background”. hat would let it run at full capacity even when alt tabbing.
it is a problem though why it cannot register that it is being used - and should allocate that cpu power to itself.