AMD’s Older RDNA GPUs Benefit From Smart Access Memory Support

When AMD announced it had added Smart Access Memory support to its older RDNA GPUs, we weren’t sure how much benefit gamers could expect to get out of the feature. RDNA and RDNA2 are quite similar, microarchitecturally speaking, but there are some significant differences in memory latency, cache design, and available VRAM bandwidth.

Overclock3D recently put the 5700 XT through its paces on a range of games and confirmed that the GPU sees an impressive uplift in some games. We were curious to see how the 5700 XT’s gains compared against RDNA2-equipped cards in general terms, so we consulted TechSpot’s 35-game test of Smart Memory Access. While Overclock3D and TechSpot don’t overlap much, they did both test Watch Dogs Legion, Assassin’s Creed Valhalla, and The Witcher 3.

The behavior pattern observed for RDNA is similar to RDNA2. A handful of games like Assassin’s Creed Valhalla are genuinely faster; the average 1440p frame rate for ACV rises from 69.7fps with SAM disabled to 76.1fps with the feature enabled. Forza Horizon 4 is as much as 1.21x faster in 1080p.

Not every game cares. Microsoft Flight Simulator and Days Gone see no benefit from the feature. While a few titles do perform worse with SAM enabled, none of the games Overclock3D tested lose more than a percent or two. The net effect of the feature in their test suite is strongly positive.

There is some indication that RDNA does not benefit quite as much as RDNA2 from Smart Access Memory. Of the three games TechSpot and Overclock3D both tested, the 5700 XT’s gain in Assassin’s Creed Valhalla was about half the size of the Radeon 6800’s. TechSpot reports a 4-9 percent gain in The Witcher 3: Wild Hunt for the Radeon 600, while Overclock3D reports performance as flat. This could be explained by differences in benchmark methodology between the two sites or by a difference in testbed configuration.

But even if RDNA doesn’t pick up quite as much performance as RDNA2, all indications are that AMD owners with RX 5xxx GPUs should update their drivers and motherboards if necessary and give Smart Access Memory a try. 2-8 percent in some games is not a huge boost, but at a time when new GPUs are running as much as 1.7x above MSRP, we’ll take any improvement for existing hardware we can get.

We may see more game developers turning to technologies like FSR, DLSS, and enabling improved performance under Smart Access Memory / Resizable BAR (that’s the generic name for the feature) if GPU prices remain high. While there is a limit to how much increased efficiency can compensate for old hardware, these techniques do collectively offer the potential for 20-50 percent increased performance for a modest quality hit. If GPU prices remain stuck in the stratosphere for another 12-18 months, we may see more developers quietly optimizing for older hardware more than they once did.

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