Question AMD A10-5800K stuck below 2.5 Ghz

[Moribund]

My customer's CPU. I built this machine for him in 2013. The CPU had no issues when turboing to 4.2 GhZ. Back then it had Windows 7 on it. This year he wanted upgrade to 10. But now the CPU is stuck at low clock speeds. It's in high performance mode both in BIOS and in Windows. Not only that but I tested it with AMD Catalystand overclocked it to 4.4 Ghz. When the system boots - the CPU is at 3.9 GhZ. Then it falls to 2.47 GhZ at 65% utilisation(according to Windows Resource monitor. At the same time Speedfan shows 100% utilisation. Whenever I play a high quality video - The clock falls to 1.0 GhZ. (Using CPU graphics, no dedicated GPU). What's throttling down the CPU? Temps are below 50 C Even when stress testing with Prime95 - I get exactly the same picture.

What is weirder yet. As soon as I stop all the applications, close browsers, basically go to idle, - clock speed jumps to 3.6, and remains there for a minute or two then drops to about 2 Ghz. Something is throttling it, but it's not temps. No idea what it could be.

Any ideas guys? Thanks

 

[Moribund]

Oh One more thing: When Prime95 Torture testing Test1 88000 LL iterations of M383553 using FMA3 FFT length 192 K, Pass 1=768. Pass 2=256, clm=2 I get FATAL ERROR warning Final result was 000000000, expected: E3CA2E29. Hardware failure detected. And Windows Resource monitors is only showing 2 cores when there should be 4.

 

[Deleted member 14196]

Did you clean install win10 or upgrade over win7?