I have a computer with an Intel 620 and openmw is unplayable while the original game is able to maintain 60 fps even with MGE XE
It seems to run over OpenGL. On high render distances, it's very sluggish.
Is it using up GPU time or just maxing out CPU? It uses OpenSceneGraph, which has some very slow state management (std::map and atomic reference counting all over the place) in its render thread so I wouldn't be surprised if you are stuck with a single core at 100%.