Friday, July 8, 2011

Using High Performance RAM with AMD A-Series APUs in DX11 Gaming

The Lynx GPU

In recent weeks we’ve been really excited to see the discrete-class performance of AMD’s new A-Series APUs, where a multi-core CPU and a full DirectX11 GPU basically sit side by side on one piece of silicon. This means that users can get fairly solid 3D gaming performance out of their rig using the onboard graphics alone.

Like all of today’s graphics processors, the Lynx GPUs that reside on these Llano APUs are also reliant on the memory sub-system to reach decent performance levels in today’s 3D games. This is because modern GPUs use parallel processing to churn through large data sets on-the-fly, using accelerated pixel and vertex shaders to make these realistic 3D environments come to life. Memory bandwidth, or basically the speed of your RAM, is therefore a crucial factor in getting this data to and from the GPU.

The upshot of all this is that if you use high-performance memory with your A-Series APU, the onboard Lynx GPU will have more bandwidth to play with, resulting in faster frame rates and smoother game-play in modern 3D games.

To give you a clearer idea about just how much extra performance you can expect see by using high-performance RAM, we’ve done some benchmarking and testing which we will share with you here.

Raising the Memory Clock

We took AMD’s A8350 APU, our GIGABYTE A75-UD4H board and tried a variety of differently clocked memory modules. We wanted to see exactly what effect raising the memory clock had on DX11 3D gaming performance. For this we used a variety of Corsair RAM modules; DDR3 1333, 1600, 1866, 2000 and 2400.

And just to make interesting, we also benchmarked the DDR 2400 rig with HiCookie’s overclocked GPU settings – to take a glimpse of the outer limit of A-Series APU performance.

Here are the test configurations we used.


Board RAM

Here are the benchmarks of four DirectX 11 titles that we enjoy playing; Dirt 3, Dragon Age II, Metro 2033 and Civilization V.





As you can see, you can expect to enjoy a decent performance boost with each successive memory clock increase. Civilization V stands out an example of how even relatively affordable DDR 1600 RAM can be used to effect a FPS change of huge significance – moving from 28 FPS to a much smoother 47 FPS. In short, APU users who invest in high-performance memory will be getting more performance out of their AMD APU – in 3 out of 4 cases we explored, that performance boost was pretty much incremental.

Overclocking Does Make a Difference

A few reviewers in the last week or so have concluded that AMD’s Llano APUs are entirely bandwidth constrained, and that overclocking the APU is more or less a waste of time. We attempted to explore that idea by getting our resident overclocker HiCookie to try and push the Lynx GPU on a higher RAM clock. The results here speak for themselves. Using our A75-UD3H board with HiCookie’s overclocked GPU settings, you’re entering another performance bracket entirely, with often double the frame rates of stock settings. If you’re going to use DDR 2400 RAM, there‘s clearly GPU headroom worth exploiting.

A Word to the Wise

So if you’re thinking of building a AMD A-Series rig anytime soon, bear in mind that the RAM you choose will have an effect on gaming performance. High performance RAM will allow you to get more out of the onboard Lynx GPU. But hey, don’t forget that you’ll probably have to configure the memory timings in BIOS according to the manufacturers recommendations (usually printed on the DIMM itself). SPD alone won’t get you there!

Good luck, and good gaming…

You can read this blog in Chinese (中文版) here.

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