Not combat but XPlane 10 was said (by the developer) to use up to 20 threads. One for each plane and in version 11 the cars on the streets use some..
More recently they pointed out:
Three Performance Optimizations for X-Plane 11.02
"we have been steadily adding more multi-core work for the last few years, and we’ll be adding more in future X-Plane 11 updates. For example, X-Plane 10.50 re-structured the renderer, separating the work of discovering what to draw (“culling”) from the work of actually drawing. In X-Plane 11, we can do that culling on multiple cores, improving total framerate."
The article does indicate its done for FPS and makes a difference. I haven't noticed how many total threads they are using now (was 20 in previous writing).
XPlane 11 Development Article Cores and threads are the future of high reality simulations. Some are already there (e.g. XPlane).
FWIW.
