With AMD processors, you have a choice of overclocking via the multiplier alone (provided you have an unlocked chip), via the CPU bus alone if you wish to do so. If you have a locked multiplier, you will be limited to CPU bus overclocking only as well. If you have an unlocked chip like we do, you can choose to use a combination of the two as well. Overclocking with a combination of the two is generally a preferred method as it will provide increased benefits compared to just overclocking via the multiplier alone. It allows the chip to run quicker internally as well as overall.
One vital bit of information to remember is that voltage is key to getting a successful overclock. Too much voltage can harm the stability and subsequently it will produce lower scores than it is capable of. Too little voltage and it will be unstable. Finding the sweet spot is essential on Bulldozer and it may take some time until you get it just right.
During the overclocking, we will be testing the following:
Default speeds
We will be using the BIOS defaults to see how the motherboard manufacturer has configured their BIOS for comparison reasons.
Maximum CPU bus overclocking
This is tested to show you which motherboard can take your CPU to the highest bus speed and hold it there. This is not strictly for 24/7 use, it is just to set the benchmark to compare motherboards against each other.
We will be using the BIOS defaults to see how the motherboard manufacturer has configured their BIOS for comparison reasons.
Maximum CPU bus overclocking
This is tested to show you which motherboard can take your CPU to the highest bus speed and hold it there. This is not strictly for 24/7 use, it is just to set the benchmark to compare motherboards against each other.
We won't be overclocking via the multiplier alone because there is not much chance that swapping a motherboard out will allow us to get another 100 or 200MHz out of the CPU.
Getting the system to boot at 300MHz on the CPU bus was a doddle, and even higher than that required little effort to get the machine stable. We managed to get the CPU to top out at 335MHz and after tweaking to no end, it would not go any further. We have most likely hit the limit for the CPU and/or motherboard on the current cooling we have. With that in mind, our final clock speed which was benchmark stable and could handle over an hour of continuous loading by the x264HD benchmark was a respectable 4523MHz or in other words, a 46% overclock.
