sorry i m from germany ( bad englich)
I had the same problem.
i fix the cpu speed to the max cpu speed. (bios)
before the cpu ratio on 0,87 ghz (quad core) 12-23 fps on min
now cpu ratio on 3,7 ghz on all cores 72-86 fps on max
not clocked automatically to the max cpu speed
xenon 1230 v3
gtx 970
8gb ram