Testing Different Memory Speeds on AMD’s A8-3850 Llano APU

Sisoft Sandra 2011 SP3

The Sisoft Sandra 2011 SP3 benchmark utility just came out a few weeks
ago and we have started to include it in our benchmarking. Sandra 2011 comes with
support for Virtualisation (Virtual PC/Server, Hyper-V, VMware) and
GPGPU (OpenCL, DirectX 11 DirectCompute), but today we will be using the
program to look at memory and CPU performance!

Results: Our test system uses the AMD A8-3850 ‘Llano’ APU and as you can see from the Sandra Memory Bandwidth test results the memory clock speed greatly impacts the memory bandwidth. The 2x4GB 1333MHz CL8 memory kit was able to hit ~12.7GB/s memory bandwidth. Moving up to the 2x4GB 1600MHz CL8 memory kit we saw the bandwidth jump up to ~15.0GB/s, which is a 18% improvement over 1333MHz. The jump up to the 2x4GB 1866MHz CL9 memory kit was only 1GB/s, but we had to loosen the timings from 8-8-8-24 1T to 9-10-9-28 1T and the looser timings always hurt performance. Running the 4x4GB 1866MHz CL9 memory kit offered the most performance as once again we found that this AMD APU loved having all the memory banks occupied and with more memory lanes available for the APU the performance was able to improve.

Since we are looking at memory performance in this article we felt that memory latency needs to be looked at, so we ran the Sandra Memory Latency benchmark to see what the performance looked like.

Results:
We found that the 1333MHz memory kit had a memory latency of 86.8ns, 1600MHz was at 80.1ns and 1866MHz was 76.2ns. It was a bit odd to see the 4x4GB 1866MHz CL9 kit running slower than the 2x4GB 1866MHz CL9 kit, but the difference is not significant or a concern.