AMD Radeon RX 6700 XT review: A good GPU that (understandably) costs too much

Smart Access Memory performance

We tested our entire games suite with AMD’s Smart Access Memory feature both on and off. It’s a killer new technology that requires some technical explanation.

Smart Access Memory, introduced for AMD’s Radeon RX 6000-series and Ryzen 5000-series processors, gives the CPU full access to the GPU’s memory, rather than limiting it to the usual 256MB chunks. That unrestricted access to the data channel can improve gaming performance. The technology is built upon the PCIe standard’s optional Resizable BAR feature, which allowed Nvidia and Intel to follow in AMD’s footsteps by activating Resizable BAR via BIOS updates on their hardware.

AMD

Smart Access Memory can’t be used by everyone, though. You need a Ryzen 5000-series processor and a compatible X570 or B550 motherboard that has had its BIOS updated to support AMD’s AGESA 1.1.0.0 firmware or newer, along with a current version of Radeon Software (which you need to run the Radeon RX 6000-series anyway) and a 64-bit operating system. Soon, BIOS updates will bring SAM to Ryzen 3000-series processors as well. Several modern Intel motherboards have rolled out BIOS updates with Resizable BAR support for 10th-gen Core processors, though support varies from vendor to vendor and even board to board. AMD tells me that “Radeon RX 6000-series GPUs will work on any resizable BAR-enabled CPU,” so the increased performance you see below for the RX 6700 XT should also work on compatible Intel systems.

Compatibility keeps expanding, but most people won’t have SAM-capable gaming systems yet, especially with how difficult it’s been to obtain Ryzen 5000 processors in today’s market.

Gordon Mah Ung

For now, compatible motherboards also won’t enable Smart Access Memory by default. You need to dive into your BIOS’s advanced settings and activate both “Above 4G Decoding” and “Re-size BAR support” to coax it into working. AMD expects AM4 motherboard makers to turn on Smart Access Memory by default soon, however, and it’s expected to become standard on Intel’s next-gen Rocket Lake-S 11th-gen hardware as well.

The performance uplift from Smart Access Memory/Resizable BAR varies from GPU to GPU, game to game, resolution to resolution, and even depending on the graphics preset you’re using. The 1440p results for the Radeon RX 6700 XT below don’t map exactly to the gains and losses we saw with the beastly $1,000 Radeon RX 6900 XT with SAM enabled, for example. It’s variable enough that Nvidia limited the RTX 3060, the first GeForce GPU with Resizable BAR support, to only eight whitelisted games out of the gate.

AMD, on the other hand, lets Smart Access Memory do its work with any game, even though it may result in a very minor performance hit in rare circumstances. “AMD has focused on maximizing performance for gamers with Smart Access Memory,” a company spokesperson told me when asked about the difference. “With AMD and the broader industry embracing ReBAR on modern platforms, we’re focused on enabling as many gamers as possible to take advantage of the extra performance on offer with Radeon + Ryzen and similar platforms.” The results below show that it’s probably worth it for most people.

Brad Chacos/IDG

As you can see, Smart Access Memory provides extra performance across most of the board, but the significance varies wildly. Some games see little extra oomph; Borderlands adores SAM, showing much higher performance with it active; and Gears Tactics and Horizon Zero Dawn actually lose a few frames with the feature active, though only at 1080p resolution. SAM’s extra boost is enough to propel the 6700 XT past the RTX 3070 in some scenarios where it otherwise loses by a hair, and help it pull ahead of the RTX 3060 Ti in many games. But on the whole, it doesn’t change the overall performance picture aside from in a handful of highly reactive titles.

Next page: Ray tracing performance