The FX-8320 has a base clock of 3.5 GHz. and 4.0 GHz. Turbo mode.
The newer CPUs and APUs have a very complicated internal control that varies the operating frequency dynamically based on the processors temp and load. As long as Turbo mode is enabled in your mobo BIOS, the CPU will use up to and including the 4.0 GHz. Turbo frequency under the right conditions. It may be for a split second or for several seconds as it changes constantly based on the complex algorithm.
As far as overclocking is concerned it's understood that ANY overclocking efforts immediately void the warranty because you are operating the CPU/APU/GPU beyond the mfgs. settings. With that in mind most quality PC hardware suppliers leave a safety margin in their products to insure long life. I personally have been overclocking CPUs for 15+ years and I have never had a CPU fail - ever. I don't go crazy with the overclocking or abuse the processor with excessive voltage or inadequate cooling like some folks do. Only those who are willing to accept damaged PC hardware and immediately loss of their warranty should consider overclocking.
Your CPU running in Turbo mode is not overclocking and it has no impact on your warranty. The Vishera based FX CPUs are powerful processors and great fun.
Building a reliable PC involves more than just assembling the parts. You need to be able to configure all of the BIOS settings appropriately. This can be quite involved and frustrating as it can require a lot of trial and error with stress testing. It is however often the only means to get a 100% reliable PC.