http://www.lazygamer.net/general-news/nvidias-gtx970-has-a-rather-serious-memory-allocation-bug/ If you have a 970 you may want to run the benchmark.
I wonder if the SMM's are more tied into the memory bus than people realized and that is what is holding the 970 back. Only differences between a 980 and 970 are the three disabled SMM units. Same memory bus and vram size.
I hope this doesn't affect 980s too. I really don't want to have send mine in if a recall is issued. But some people in one of the reddit threads said had the issue to with 980s.
Seems like the people posting bad scores with 980's and other cards are running the GPU as their primary device instead of running off another GPU for the display. Using the card being benchmarked means Windows and maybe some other apps like a web browser have things loaded into vram that are making a slowdown show up.
Guess that idea goes out the window. A 4GB 980M has 4 SMM's cut and it does not have a slowdown problem.