Overclocking on Ryzen is not all that hard, but something new to us. It is done much like you would do it on Intel systems. Luckily ASUS has a built in overclocking profile already saved in the BIOS on the Crosshair VI Hero motherboard. All you have to do is go into the Extreme Teaker tab and then into the Overclocking Presets menu. Here you can enable the 4.0 GHz OC profile.
What the OC Profile does is puts the overclocking tuner on manual, changes the BCLK frequency to 100 and the CPU Core Ratio to 40. While these settings worked and we were able to boot into Windows this setting for some reason was not stable when we went to run our stability test. Our system would reboot every time we put a big load on the CPU. Going back into the BIOS I simply changed the CPU Core Ratio to 39 and tried again.
This turned out to be 100% stable with all cores rocking at 3.9 GHz. Temperatures were pretty normal too as you can see from the screenshot below.
It was quite odd to me that 3.9 GHz was so stable and 4.0 GHz seemed completely unstable. I would say this has a lot to do with how early we are into this platform and of course the chip we received as well. Other factors can be the motherboard you are using as well as the revision of BIOS. But as the platform matures I think we should see some very high overclocks on Ryzen.