How much does faster memory help the new AMD APUs?
Memory speed is not a factor that the average gamer thinks about when building their PC. For the most part, memory performance hasn't had much of an effect on modern processors running high-speed memory such as DDR3 and DDR4.
With the launch of AMD's Ryzen processors, last year emerged a platform that was more sensitive to memory speeds. By running Ryzen processors with higher frequency and lower latency memory, users should see significant performance improvements, especially in 1080p gaming scenarios.
However, the Ryzen processors are not the only ones to exhibit this behavior.
Gaming on integrated GPUs is a perfect example of a memory starved situation. Take for instance the new AMD Ryzen 5 2400G and it's Vega-based GPU cores. In a full Vega 56 or 64 situation, these Vega cores utilize blazingly fast HBM 2.0 memory. However, due to constraints such as die space and cost, this processor does not integrate HBM.
Instead, both the CPU portion and the graphics portion of the APU must both depend on the same pool of DDR4 system memory. DDR4 is significantly slower than memory traditionally found on graphics cards such as GDDR5 or HBM. As a result, APU performance is usually memory limited to some extent.
In the past, we've done memory speed testing with AMD's older APUs, however with the launch of the new Ryzen and Vega based R3 2200G and R5 2400G, we decided to take another look at this topic.
For our testing, we are running the Ryzen 5 2400G at three different memory speeds, 2400 MHz, 2933 MHz, and 3200 MHz. While the maximum supported JEDEC memory standard for the R5 2400G is 2933, the memory provided by AMD for our processor review will support overclocking to 3200MHz just fine.
Both of our synthetic graphics benchmarks show fairly linear scaling between memory frequency and graphics performance.
The increase from DDR4-2400 to DDR4-2933 saw an 8% and 6% difference in 3DMark and Unigine Superposition respectively. Moving to DDR4-3200 saw impressive scaling of 13% and 11% from the slower DDR-2400.
Just as we saw in our synthetic benchmarks, real-world gaming examples show scaling of 10-15% moving from DDR4-2400 to DDR4-3200. DDR4-2933 provides a 5-7% performance boost compared to DDR4-2400.
Single Channel vs Dual Channel
Of course when we are talking about memory performance, and especially with APUs, the idea of using one DIMM in a single channel configuration v.s. two in a dual channel configuration is a big topic.
While lower-end system builders can get away with the usually cheaper Single DIMM option on other platforms, that's simply not the case for gamers looking to really take advantage of the graphics on their R5 2400G.
Historically, we've seen reasonably linear scaling of frame rates with memory speed increases for AMD APUs for gaming. This doesn't change with the new Ryzen and Vega-based APUs. Increased baseline memory compatibility to DDR-2933 with the Raven Ridge platform provides nice advantages in allowing all users to achieve higher memory clocks without having to overclock RAM and depend on motherboard compatibility with certain memory speeds.
We also tested allocating additional memory to the Ryzen part within the BIOS. Going from the default allocation of 1GB to the highest available on 2GB saw no performance advantage. It's clear that the Raven Ridge platform is able to allocate additional system memory as needed while gaming. However, allocating more memory in the BIOS can be useful for games that do checks for video memory either at the time of launching the executable, or when enabling higher visual quality settings.
Currently, with highly inflated prices for all DDR4 memory, a 2x8GB kit of DDR4-2400 memory will run you about $160. For around $20 more, you can get a kit of the same capacity that will support DDR4-3200. For users looking to game on the integrated GPU of the Ryzen 3 2200G or Ryzen 5 2400G, it seems like a no-brainer to opt for the faster memory.
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