Like stumped pointed out, please read the sticky..
On the other hand, and for knowledge only, the FXs have some issues reading temps correctly. It's because it uses an equation to "read" the temperature, instead of having an actual physical sensor embebed.
A hint of what I said is the fact that, according to AMDs papers, the ultimate temp for FXs are in the 60s, around 65, before it shuts down itself if reaches the 70s. If you get temp readings of 75°C without any shut down, then you get an actual idea about it.
For example, after a series of test with OCCT, I got even 80s°C on all cores before I stop the test. User stop it, not the CPU itself. Ergo, the readings are wrong. How much is the gap?.. Well, according to the sticky stumper pointed out, it "should" be around 10°C between the readings and the "real" values.. If you ask me, I think is even more..
Bottom of all, there's no way (in my opinion) to know the "exact" value of temp. I use 4 different software to read the CPU temps, and all of them reports almost the same values. Maybe a gap of 3-5°C between them, including AMD OverDrive. If you can and want, do your own test an check it..
My advice: get a better aftermarket CPU cooler. I have an H80, but just purchased a Corsair H110 to see if I can get higher speeds.. But that's just me...
8320 @ 4,7 / 990FXA UD5 / 7950 @ 1100-6000 / Switch 810 / H110 p-p / 16 GB RAM / 23" 5760x1080 / SSD 64GB RAID0 / HX750 / SB Recon3D Fatal1ty Champion / z506