I'm seeing a number of bug reports where weird artifacts are showing up in 940...missing pieces of runway, flickering triangles...all sorts of good stuff!
I believe that this is due to some kind of bug relating to threading, X-Plane and the video drivers. I won't say whose fault it is because I really don't know. I do know that the bug appears to not happen on OS X. (But this could simply be because the threads time out differently on OS X.)
The changes to the rendering engine for 940 from 930 are substantial and aggressive - it'll take us a little bit to fix these things.
When you wonder how come programs don't use all 8 of your cores yet, well...this is why...multi-core programming is complex, tricky, tedious to debug, and often involves substantial changes from the original code.