I have a i5-760 overclocked to 3.5 GHZ with Gigabyte GA-H55M-D2H motherboard. After overclocking i have run all the tests of prime,OCCT,cinebench all of them didnt show any error but after some time of normal usage or gaming usage sometimes CPU freezes & i am unable to shutdown from shutdown switch only option is to cut the power supply from UPS.
It also make some screeching voice in speakers.
Can you guide what could be wrong it a wrong overclock.
The cpu can be cool but the power vrm on the board that acts as a power supply to the cpu can get very hot. It does get very hot on some boards that lead to a lot of issues. Those little black squares near the cpu that are tiny, those are mosfets and they convert 12v into a lower voltage but at a higher current for the cpu to use. Once they get to hot they don't provide rated current or fail outright.
At stock the cpu will average around 95w as that is what Intel has it rated for but as you overclock and have to raise voltages as you push 3.8 to 4ghz the power consumption easily more than doubles. 200w is not uncommon. Power supplies can handle the load but the boards don't.
It really depends on the sample (your cpu) that you bought and how good its quality is. Not all are equal but you need to look at the guides for this platform. I think that should be able to pull off 3.2-3.5ghz without to much trouble but the board is the reason that you won't get far. If you had a quality board 3.8-4.4ghz would be possible.