For a while now, high speed memory has been a bit of a luxury. The baseline or sweet spot for system performance doesn’t seem to have moved much over the lifespan of DDR3; with Nehalem, diminishing returns were had after 1333MHz, while Sandy Bridge, Ivy Bridge, and virtually AMD’s entire lineup hit their stride at 1600MHz. Yet as technology continues to advance and DDR3 continues to mature, increasing memory speed and bandwidth becomes relevant again.
When overclocking, most people typically start with the CPU, and then if they’re feeling a little more adventurous, they might work on the GPU. But either overclocking the memory or even opting for higher speed memory than we’re traditionally used to can start to pay dividends, and that’s especially true when you’re talking about AMD’s Trinity and Richland APUs. Because while Intel’s IGPs (outside of Haswell’s monster Iris graphics hardware) since Sandy Bridge have been mostly in lockstep with the memory bandwidth available at the mainstream, Trinity and Richland have remarkably powerful graphics hardware built into them, and that hardware thrives on faster memory. In fact, the graphics cores on these chips are more often memory bandwidth limited than anything else. If you’re willing to spend up or even just tweak your existing memory, there’s definitely room to extract a healthy performance boost.
We did some testing without overclocking the CPU or GPU parts of the AMD A10-5800K. Recognizing that this chip is technically last generation, it bears mentioning that the current A10-6800K is really just a very minor tweak on the 5800K, featuring an identical memory controller and identical graphics cores. The Richland APUs are essentially just Trinity APUs with finer grained power optimization. To get a good performance spread, we tested StarCraft II (which is predominately CPU limited), Tomb Raider (which is predominately GPU limited), and BioShock Infinite (which tends to fall in between). We also tested in 3DMark and did a couple of rough and tumble FRAPS runs in the Battlefield 4 Beta. Finally, testing was done at 1366x768 using the Medium/Normal presets in each game, and again at 1600x900. These are settings appropriate to the APU.
First, we ran our 8GB of Dominator GT DDR3 at 1600MHz, the traditional standard for most mainstream builds. Then we clocked it up to its spec of 2133MHz, roughly 33% faster.
Going from DDR3-1600 to DDR3-2133, 3DMark shows an 11.7% performance increase in Ice Storm, 8.3% performance increase in Cloud Gate, and 10.1% performance increase in Fire Strike, none of which are small gains. Synthetic testing actually undercuts real world results; real world gaming situations present substantial performance improvements across the board. At 1366x768, StarCraft II is up 10.5%, Tomb Raider is up 12.4%, and BioShock Infinite is up 13.8%. Even Battlefield 4, which seems to be primarily shader limited, still gets a 14% improvement. StarCraft II is inherently CPU limited and still gets a healthy bump; the rest of these boosts in performance are pretty pronounced.
When you go up to 1600x900, StarCraft II is still up 9.5%, Tomb Raider is up 14.8%, and BioShock Infinite is up 14.6%, pointing to the increased load on memory bandwidth commensurate with the increase in resolution. Only Battlefield 4 shows no improvement, possibly GPU or CPU bound.
Again, remember that these performance measurements were done with the A10-5800K running at stock speed. Overclocking the CPU cores may give the GPU some breathing room to utilize more memory bandwidth; alternatively, overclocking the GPU is invariably going to put additional stress on the memory since GPU performance seems to be governed heavily by memory speed. The sky isn't the limit, but there's still untapped performance here.
Recognizing that AMD’s A-series APUs are mainly a budget play, you don’t necessarily need to buy our high end Dominator kit to get the most out of them. Forums across the internet are alight with reports of people taking our mainstream Vengeance DDR3-1600, applying a little voltage, and getting it up to DDR3-1866 or better with relaxed latencies similar to what we tested with. If you’re doing any casual gaming on an A-series APU, though, just playing with memory speed is a quick and dirty way to extract a meaningful boost in performance and potentially allow you to even bump up settings in-game.