Power and Overclocking
Kaveri is built to be more power efficient than the previous generations of APUs from AMD. This comes from a combination of design and process technology. The 6800K is a 100 watt TDP part while the 7850K is slightly lower at 95 watts TDP. AMD has also worked quite a few firmware and software tricks to make power go down even more.
At idle all of the chips were in the same general vicinity, but we did see a pretty significant drop with the 6800K going from the older F2A and onto the G1.Sniper A88X. 5 watts at idle is fairly significant. The 7850K was right around there with 42 watts.
At load the differences are night and day. The 6800K pulls 38 watts less at load on the G1 board than the older F2A. The 7580K is a full 32 watts lower at load than the 6800K. AMD did prioritize graphics performance and power consumption over the CPU portion, so Kaveri does have the downclocked CPU core as well as process level decisions to improve power for the graphics portion. Compromises were made, and the CPU sort of got the shaft. Still, Kaveri is a very power efficient part as compared to the older Richland chips.
Overclocking AMD’s APUs can be a little bit annoying. The primary issue is that the CPU portion typically does not overclock that well. On the bright side, the graphics portion overclocks very well! Unfortunately, that graphics portion is still more memory bound than AMD would like to admit. In OpenCL applications where data can be stored in caches, overclocking results in very positive results. In gaming applications the results of overclocking the graphics portion are not as large as one would expect, unless they also overclock the memory to 2400+ speeds.
The 6800K overclocked nearly the same on both boards. On the F2A it could be pushed to 4.7 GHz, while on the G1 it could get to 4.6 GHz. The GPU portion could attain 1 GHz on both boards without issue. The 7850K is not a tremendous overclocker. I was able to get to 4.5 GHz with a bit of trouble, but the graphics portion did make it up to the 1 GHz mark without any real issue.
Once the base bus clock went over 105 MHz, errors started to occur. First there are AHCI issues, and then it spirals from there. For best overclocking results, users absolutely have to use unlocked/K series APUs.