Mysterious Gaming performance cut in half

[Jman]

My friend's computer out of no where ended up performing half as well in games as it normally had for months.  Here are the specs: i5 4690k, gtx 780, wd blue 1 tb, 8 gb corsair ram, and asrock z97 pro4 mobo.  I tried to troubleshoot it by updating all of his drivers and upgrading his windows 8.1 to windows 10, but it changed nothing.  Metro Last Light is getting 20 to 30 fps on max settings compared to the 60 to 70 he would normally get and is what I would expect from his particular set up.  I decided to run a 3D mark 11 test to get a feel for how bad it was.  On firestrike 1.1 he got a 9938 graphics score but a 1414 physics score which is god awful for a 4690k.  This leads me to suspect it has something to do with his cpu, but I don't know if other components could interfere with the physics score.  Any insight on the situation would be appreciated! :]  (I am currently going to try and place his 780 in my rig with quite similar specs and see how it performs to isolate where the problem is coming from)

[Marcus Torre DeProspero]

The CPU is screwed check the voltage and clock speed my old fx 4300 got 8000 on the physics but your 4690k get 1000 that's not right

[Jman]

Opened up the bios. Here's the voltages. All seems stock to me CLOCK speed: 3.50

[BrightCandle]

Could be overheating or on low power saving mode in windows.

[Husky]

Opened up the bios. Here's the voltages. All seems stock to me CLOCK speed: 3.50

Turn Intel SpeedStep and CPU C States off in the BIOS.

Also change the power options in Windows to High Performance