The maximum Operating Temperature of the A8-7600 is 71.3C (http://www.cpu-world.com/CPUs/Bulldozer/AMD-A10-Series%20A8-7600.html )
If the you know for certain it is the APU that is overheating, it could have several reasons:
1) The thermal paste between the CPU Cooler and APU is old and not conducting heat as effeciently
2) Dirty CPU Cooler Fins or bad CPU Cooler Fan (Defective CPU Cooler)
3) CPU Cooler not installed correctly or loose and not making proper contact with APU.
4) Poor air circulation in Computer case. (dirty vents or all fans not working)
I would use a monitoring software to check the APU temperature and see if it goes above 72C while under load. I would also take a physical look at the CPU Cooler fan to see if it is working correctly with the side panel off.
With the side panel off, press down on the CPU Cooler with the computer powered on and see if the temperature goes down. If it does it indicates the CPU Cooler is not making proper contact with the APU.
Run a stress test on the APU to verify it is overheating and not something else. OCCT is one that I personally use to stress test the CPU, GPU or the PSU. But there are others as good or better.
