Since the 6800K has an unlocked multiplier, setting the multiplier to 48, upping the voltage a bit, and booting the system at 4.8GHz was incredibly simple. What came next was more complicated.
To test stability, I ran Prime95 and monitored temperatures with MSI ControlCenter software. The big tower cooler I installed on the 6800K easily kept temperatures in check; they never got higher than 59° C. However, the MSI software showed that, intermittently, CPU speeds were dropping down to 3.2GHz or so. Hmm.
I thought maybe the MSI monitoring software wasn't reporting the CPU temperature correctly, but a quick series of finger tests on the CPU cooler and the motherboard VRM heatsinks told me that overheating was unlikely. After puzzling over it for a while, I noticed that the MSI motherboard was giving the 6800K quite a bit more voltage than requested. I had the BIOS set to 1.5V, and ControlCenter reported voltages as high as 1.608V. That's a lot of juice, and I suspected that the motherboard was doing some throttling to keep the CPU from exceeding a power limit.
Sure enough, reducing the CPU voltage seemed to reduce the amount of throttling. I also set the BIOS option labeled "Core OCP Expander" to "Enhanced," which seemed to help. Eventually, I found a stable config at 4.8GHz and 1.475V that produced only minor, occasional throttling in ControlCenter with Prime95 running. (Going below 1.475V led to lock-ups and blue screens.) The MSI board still ran the CPU voltage a little hot, reading as much at 1.576V under load, but CPU temperatures remained below 60° C. I figured I could run a few tests and see what my overclocking exploits had gained me.
Frustratingly, when I ran several benchmarks like Cinebench and x264 encoding, my overclocked 6800K appeared to be throttling more than expected. It was sometimes slower than the stock speed. 7-Zip fared a little better, but the performance gains weren't terribly enthralling.
I suspect the A10-6800K could be overclocked further with a beefy water cooler, and either the right BIOS tweak or swapping in a different motherboard might help eliminate the throttling. Still, for the average guy looking to extract a little extra performance out of a CPU without too much extra expense, the 6800K doesn't appear to have lots of easily accessible clock frequency headroom. Our sample doesn't, at least.