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Quad-channel RAM vs. dual-channel RAM: The shocking truth about their performance

Gordon Mah Ung | Sept. 14, 2015
Stop arguing. Benchmarks don't lie. We tested both kinds of RAM in the same PC. Check our charts to find out more.

me tower side
I simluated dual-channel performance using this MicroExpress B20 system with its X99 chipset and Core i7-5820K chip.

Sisoft Sandra Memory Bandwidth

My first test was SiSoft Sandra’s memory bandwidth test. This jack-of-all trades benchmark suite measures and pokes just about everything in your PC. It's long been a standard to measure available memory bandwidth in a PC. The results were as expected (and also a good way to double-check that I hadn’t put the modules in the wrong slots). Going from dual-channel DDR4/2666 to quad-channel DDR4/2666 nearly doubles the available memory bandwidth. Woohoo! Go home, right?

Nope. This chart is probably the only good news for quad-channel memory, but I’ll let you bask in the bandwidth for now. Read on for the real performance impact.

memory bandwidth sisoftsandra
Sorry, dual-channel RAM: Quad-channel is way better. Click on image to enlarge.

Encoding performance

Synthetic tests measuring the theoretical performance is one thing, but just where does it show up in real tasks? To find out, the next test I threw at the system was Handbrake. A popular and free video encoder, it’s a CPU-heavy test. As video encoding is something that’s believed to be bandwidth-sensitive, I thought doubling the memory bandwidth would pay off big-time. Unfortunately, if you look at the chart below, I saw zippo. I was quite surprised, as I’ve long believed memory bandwidth helps encoding performance. I’ve actually seen it in the past on older hardware platforms, too, so this was a shocker. I will say: This isn’t the last word, as different encoders and different encoding loads could favor the increased bandwidth. But today, I’m pretty disappointed.

memory bandwidth handbrake
I saw virtually no difference in our encoding test between dual-channel and quad-channel RAM. Click on image to enlarge.

PCMark 8 Creative

My next task was PCMark 8’s Creative Conventional test. This synthetic test attempts to simulate a workload of photo editing, video encoding, light gaming and browsing. I run the conventional portion rather than the GPU portion to keep the workload restricted to the CPU itself. The result was, again, pretty surprising and disappointing. 

memory bandwidth pcmark8 work conventional
PCMark 8’s Creative Conventional test shows minimal impact too. Click on image to enlarge.

PCMark 8 Home

I also ran PCMark 8’s Home and Work Conventional tasks to change up the workload. Again, nearly double the system memory bandwidth made no difference. I’m not even going to bother wasting Internet bandwidth with the chart of PCMark 8 Work’s result, because it’s the same.

 

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