Help, i have an i5 750 @2.66Hz as my cpu and an ASUS P7P55D PRO motherboard. i opened cpu-z and saw the core clock speed was 535MHz with a 4x multiplier, that's about like a quarter of the usual speed. I recently reinstalled windows 7 and i'm stuggling with this problem. I can't game anymore because it's too laggy. It wasn't that slow before. I even turned off the speedstep in the BIOS but still no luck. i'm sure i have enough power supplied to the PC.
Yup, your cpu is too hot and starts to throttle (lowering cpu speed).
Best thing you can do now at this point is to check if the cpu cooler is attached properly.
For now i would advise you to remove the cooler, remove any sign of thermal paste and get some new high grade thermal paste like arctic silver.
Then apply new paste on the processor (i usually do tiny dots on the corners and a slightly larger one in the middle) and re-apply the cpu cooler.
After that see what the temperatures do for you then, my bet is that it will allot cooler.
thanks mate it's fixed. i plugged the 4-pin power of the CPU fan into another 4-pin socket, the temp is 41 degrees now in idle. However i would get a CPU fan error during the boot up, but whatever. thanks again