Is my CPU or Motherboard bottlenecking my PC?

Hello everyone I have a system that I've built back in 2014 and had no stability problems with since. Recently with Grand Theft Auto V releasing I have noticed a huge performance degradation even in other games as well. I've tried formatting my computer and reinstalling Windows and it is exactly the same. I have updated my drivers at this moment I am currently running the latest drivers that AMD has to offer 15.7 and games stutter like no tomorrow, I also downgraded drivers and went back to 15.2 and 15.4 and noticed that performance in every game was identical. I conducted a test and ran GTA 5 and noticed that the CPU was downclocking itself to 1.33ghz even at the lowest graphical settings and lowest resolution, and the GPU usage would fall as low as 32% and dipping even lower sometimes. Even after disabling all power savings utilities I found that the CPU is still downclocking itself and saw that this did not occur at the desktop, the processor would run just fine when at idle. The temperatures are also normal 38c at idle and maxes out at 65c under load. I don't know if my chip is defective or my motherboards chipset cannot handle said CPU, I have not overclocked anything and I know for a fact that thermals are perfectly in line, Another thought that has passed in my mind is that maybe my PSU simply isn't cutting it anymore, I've heard of PSU degradation before and am sure wondering if that is what is happening with me. I just don't know anymore this problem is making all of my games unplayable with all the stuttering that is occurring on screen and I don't know which part needs replacing, The PSU, the motherboard, or just the simple fact that my CPU may just be defective. Please help anyone out there I would just like to enjoy my PC games without shelling out another large amount of money thank you

Here are my specs
CPU: AMD FX 6300 @3.5ghz (Stock cooling)
GPU: MSI Gaming R9 270X 2gb
MOBO: Biostar A960D+ AM3+ Motherboard
RAM: 8gb Samsung ddr3 2x4gb (Dual Channel) @1600mhz
PSU: Corsair CX430
Storage: 1tb WD Caviar Black
Case: NZXT Source 210
Monitor: Samsung Syncmaster S24B240 1080p 60hz