AMD Radeon RX 6800XT ‘Smart Access Memory’ on Intel Z490 motherboard?
AMD Smart Access Memory is a marketing name for a technology that existed in PCIe specifications since the second generation of the interface. AMD took advantage of a feature that wasn’t really a focus of anyone outside of Linux or server communities. With Smart Access Memory the processor is able to utilize GPU memory through an extended base address register. Some motherboards already offered this option with the ‘Re-Size BAR’ or ‘Resizable Base Address Register’ function.
Recently a new BIOS from ASUS for their Z490 motherboard has enabled this option. Simply by enabling the feature in BIOS, the AMD Radeon RX 6000 series GPUs should automatically take advantage of the feature. Japanese website ASCII decided to give this BIOS a test.
AMD never said that this feature will be exclusive to Radeon RX 6000 GPUs and Ryzen 5000 processors. However, those product lines are listed as supported on the technology page, simply because that’s what AMD tested (so far). Another reason is obviously the marketing and sales of their next-gen hardware, which at this point is completely out of stock.
Meanwhile, other vendors have been working to enable this feature for their hardware. The support is expected for other processors, motherboard chipsets, and of course the graphics cards. NVIDIA also confirmed it is developing a similar feature for their graphics cards.
ASCII tests ‘SAM’ on Intel Z490 motherboards
With the ASUS ROG Maximus XII EXTREME featuring 1002 firmware (released on November 27th), the ASCII editor was able to enable the Re-Size Bar feature in the Advanced Tab in the motherboard’s BIOS.
The editor is using Intel Core i9-10900K processors and Radeon RX 6800 XT reference model with the feature enabled and then disabled to see if there are any improvements. It is worth noting that SAM does not always bring a noticeable performance boost, even on the Ryzen 5000/Radeon 6000 platform. That said, the editor only tested the games where SAM is proven to provide such a boost: Assassin’s Creed Valhalla, Forza Horizon 4, Red Dead Redemption 2, and Rainbow Six Siege.
Assassin’s Creed Valhalla (1920×1080, Highest)
The feature shows improvement on both 1% Min framerate and the average:
Forza Horizon 4 (2560×1440, Ultra)
The editor tested the Forza Horizon 4 at 1080p resolution first, but the results were CPU bottlenecked and shown minimal gains. While the GPU-min/avg frame rates are indeed higher, the fps-avg (actual render framerate) is not showing a big improvement. On the other hand, a WQHD test shows a visible improvement (please note that the chart incorrectly mentions 1920×1080 resolution):
Red Dead Redemption 2 (1920×1080)
With the Re-Sizable BAR feature enabled the minimum framerate is dramatically improved:
Rainbow Six Siege (1920×1080, Highest Settings, 100% Render Scale)
The Rainbow Six Siege shows improvement in minimum framerate, with minimal gains on the average:
|AMD Radeon RX 6800XT on Intel Z490|
|VideoCardz.com via ASCII.jp||MIN SAM off||MIN SAM on||on/off||AVG SAM off||AVG SAM on||on/off|
|Assassin’s Creed Valhalla (1080p)||86||97||113%||120||137||114%|
|Forza Horizon 4 (1080p)||209 (GPU-min)||252 (GPU-min)||121%||220||221||100%|
|Forza Horizon 4 (1440p)||182 (GPU-min)||212 (GPU-min)||116%||210||243||116%|
|Red Dead Redemption 2 (1080p)||34||95||282%||120||129||108%|
|Rainbow Six Siege (1080p)||279||312||112%||441||443||100%|