Instances of performance deterioration under identical scene load

Let's see if we can get to the bottom of this.

Sometimes I've observed a performance differential in OpenMW scenes in excess of 30 fps, which can be the difference between playable and unplayable, or stable and unstable framerate.

Needless to say, hopefully we can verify whether the high framerate is something that can be exploited and achieved consistently, or whether it is an OS scheduling quirk and out of OpenMW's hands.