You need to use Prime 95 Version 26.6 Or below, said here:
http://www.tomshardware.co.uk/forum/id-1800828/intel-temperature-guide.html
Intel tests their processors at 100% TDP. Prime95 Version 26.6 Small FFT's is the standard for CPU thermal testing, because it's a steady-state 100% workload which runs Core 2 processors and Core i variants with Hyperthreading within +3% TDP at stock settings. No other utility so closely replicates Intel's test conditions. This is also the utility that Real Temp uses to test Core temperature sensors.
Caution: Do NOT use versions of Prime95 later than 26.6 on Core i 2nd through 6th Generation i3, i5 or i7 CPU's which all have AVX (Advanced Vector Extension) instruction sets. Recent versions of Prime95 such as 28.9 run AVX code on the CPU's Floating Point Unit (FPU) which causes unrealistic temperatures up to 20C higher. The FPU test in the utility AIDA64 shows similar results.
Core i 2nd Generation i3, i5 and i7 processors are less affected due to having fewer transistors in a larger Die with greater surface area, and a soldered Integrated Heat Spreader. Core i Pentium and Celeron variants, as well as all Core i Previous (1st) Generation and Core 2 processors are unaffected since they do not have AVX instruction sets.
Just for reference (The above)
If you believe that it is overheating, still try a different software for stress testing your CPU if you wish to see more accurate results, something like OCCT will assist you.
With your CPU cooler, are you sure the fan is running correctly along with the rest of your case fans? I know that CPU fans can be quite hard to see if they're running correctly.
You could also set up a more agressive fan curve if you wish.
PS - The 3770 does have AVX, so try Prime95 Version 26.6 or below
