High CPU Temp with 780i?

Is that the Tcase temp, or an average core temp?

What program are you using then?

In my situation, I switched from NV 650i to P35 chipset. Now my Tcase temp is basically the same from both boards. However the core temps act different. I was using tjmax of 95C, and now I need to use a tjmax of 100C, since my cores are reading cooler then my Tcase.

So I won't trust or go by my core temps especially at idle. I'd rather trust the Tcase sensor, which is read by SpeedFan as a single temp, or your MB's utility app that shows the CPU temp as a single reading. It would also be the sensor your bios uses for the health monitor.

There is a slight chance that one of the mounting pins may not be as secure as they should be, since you mention Arctic Cooler HSF.

Only advice I have on that, is to reinstall it. When you take it off, make sure the 4 handles are turned the opposite of the arrows, and that the pins are fully pulled out of the white clamps. When installing, make sure the white clamps are completely through the holes. Push down on the pin that is hardest to secure first. Once that is done, if you can look under the MB to verify that the white clamps are secure with the black pins.

If you still have temp problems, then its just perhaps the matter of having poor airflow and really warm ambient temps.

Edit:

Forgot to mention to clean the thermal grease off with rubbing alcohol, and reapply thermal grease to its instructions.

I installed my friend's heatsink but the temp was still high. I placed his identical q6600 into my board and saw much lower temperature.

I cleaned the thermal paste off of my processor very well, so I don't know what the problem might be..... The processor was fine in my 680i

going to have to bump this. I have the exact same setup the OP is talking about and having the same problem. I reseated the heatsink but it still idles at ~50c. OCCT cuts off after about 3 minutes because of the heat. After OCCT stops, it cools back down to 50c in about 10 seconds, so I am really confused. I want to add another 8800gtx in but I can't until I get the CPU temp problem resolved.