The following chart shows how well the processor is able to sustain its clock frequency, and what boost clock speeds are achieved at various thread counts. This test uses a custom-coded application that mimics real-life performance (not a stress test like Prime95). Modern processors change their clocking behavior depending on the type of load, which is why we provide three plots, with classic floating point math, SSE SIMD code, and using the modern AVX vector instructions. Each test run calculates the same result, using the same algorithm, just with a different CPU instruction set.
Overclocking is relatively easy because of the unlocked multiplier. You are basically free to set whatever frequency you desire, and that's it. Of course, you have to disable all the various limits in the processor for your overclock to actually activate.
My highest all-core maximum stable overclock using an air cooler was 5.1 GHz, with 1.33 V. The limiting factor here is the CPU voltage. The more voltage you feed the CPU to make the OC stable, the higher the temperature. At some point, the CPU will reach its thermal limit and start throttling, which keeps you from achieving higher frequencies.
Using a 240 mm AIO I could get 5.2 GHz stable, but with even more voltage, which causes CPU temperatures to reach over 95°C, right at the throttling point—despite watercooling. Definitely not worth it.