Smart Access Memory Performance (SAM)

Smart Access Memory Performance

On our architecture page, we've mentioned that AMD is introducing a Smart Access Memory feature, which we've been eyeing for a while already. In very short explaining, the processor with this feature can address the graphics card memory (in full) instead of a block that normally is 256MB. In the case of the 6800 series, this is very handy, as your processors now have full access to some exceptionally blazingly fast GDDR6 memory and can access its 16 GB of it.  There is a compromise to make, though; CSM in your BIOS needs to be disabled. The problem here is that very likely, 9 out of 10 PCs have this enabled to ensure UEFI storage support for your HDD/SSD. 

If you have CSM enabled at default on your PC, you tie your HDD/SSDs in Windows 10 towards UEFI modus. You're out of luck now; as you cannot access your storage units anymore, you will disable CSM. The only solution is to perform a clean reinstall of Windows 10 and start all over. This was the case for us; traditionally, we have CSM enabled to re-use Windows 10 OSes on an SSD to share among other X570 motherboards. That is another disadvantage btw; if you have CSM disabled, you no longer will be able to take the HDD/SSD out of the PC and re-use on another PC. You'd again need to re-install the OS.

After installing a new Windows 10, we enabled SAM by enabling Above 4G to decode and Re-size BAR support in the PCIe Subsystem settings under advanced in the ASUS BIOS. For a Gigabyte motherboard, this is located under IO settings in the BIOS for MSI that is under Advanced - PCIe Subsystem. These two features enabled are what is called AMD Smart Access Memory. Mandatory is an X570 motherboard, Ryzen Series 5000 processor, and an RX Series 6000 or newer graphics cards.

These result sets are based on the reference test.

So yes, the only title that benefits from SAM was Assasins Creed: Valhalla. The other two titles show close to the same performance. However (and we did run all tests three times on this newly installed system), the performance benefit, IF it kicks in, can be very substantial. Valhalla benefits from this greatly. So yes, this absolutely is an interesting feature to watch, observe, and if you have CSM disabled, try out. Apply the two configuration registers, reboot, and you are good to go.