My i7-920 generates too much heat at OC?

Your temps are fine for running 24/7, but they are way higher than what they should be using that cooler. Try to reseat rhe hearsink and remember to only add a little thermal paste because if you use to much it will start to insulate.

I make the following changes:

reduce the vcore to 1.225v (tried 1.2 which also works, I set to 1.225 to make sure the cpu gets enough voltage for 3.2Ghz setting)
set DRAM voltage to 1.64v (many articles says this value is absolute safe, I tried 1.5v but caused boot failure)
BCLK still 160Hz, cpu ratio still 20x

now I am getting the following number at prime95:

-------- low high
core 0: 44 68
core 1: 40 67
core 2: 44 66
core 3: 39 63

Is it possible my previous high temperature is caused by high vcore voltage, not bad heatsink installation? It is too much hassle to reseat the heatsink. I am trying to convince myself no need to redo the heatsink installation job.

Please let me know your opinion. Thanks!

I guess I really put a little too much thermal paste on top of the cpu. When I saw less paste on the edge, I squeezed a little more on top of it. I'll just leave as it is since it is fine temperature!

Now CPU is working at 3.2G and RAM at 1280MHz. If I raise the RAM ratio to 10X to make it 1600MHz, what else should I change?

Nothing, all you need to do is raise the ratio.

I read somewhere says Uncore frequency should be at least twice as high as the memory frequency. If I set ram to 10x, should I set uncore to above 20x?

Any software to check NB & GPU temperature?

Best answer selected by george2005.

Your mobo will set your uncore automatically when you raise your ram speed.

The best software to monitor multiple temps is hw monitor.

EDIT:
Whoop! Thanks alot for the best answer. You just pushed me to 50 best answers, so i will have the silver badge in a couple of hours when the system refreshes. Not that it really matters, its just kinda cool that im the first one with a silver.

damn, it did not pass the prime95 test, the computer got rebooted by itself within one hour.

Now cpu is 160x20 = 3.2Ghz
RAM 160x8 = 1280MHz
vcore: 1.225v
uncore: 1.1v
ram: 1.64v

What should I change?

vcore to 1.25. Try that and see if it will run. Watch the temps and make sure that they dont exceed 78c as well.

Something wired. In HD Monitor, CPU VCORe shows 1.22v at idle even though I set it to 1.25v in the bios. At running prime95, CPU VCORE shows at 1.18-1.2 only.

And the core temperature displayed is always 2C lower than coretemp software.

If I set vcore 1.2875v in bios, software shows 1.232v at full load.

That is vdroop... it drops the voltage when the cpu goes underload so the voltage regs dont give a spike of volage and destroy the chip.

Take the voltage in windows as the actual voltage.

Good rule of thumb, an i7 likes to stay at or under 65C, that should be your max target temp. With a good cooler, you should be able to cruise along at 3.8Ghz with minimal to no stock voltage increases.

If you can't get 3.2Ghz stable at stock I would still suspect your cooler but not all i7's are created equal. Just my 2 cents.

What is the stock vcore? In the motherboard sometimes it shows 1.26xxx, sometimes it shows 1.28xxx as normal value, and setting is auto.

at 3.8Ghz
20X multiplier
Bus Speed - 190
QPI Link - 3415

My Core Voltage = 1.35v

I think stock voltage is 1.25v

Remember to unlink your memory and turn off any turbo features, speedstep and power saving features as at this speed it is unnecessary.

My temps at idle are: 38C, 41C, 39C, 39C and don't go over 65C on full load with any core.