Uh oh.....I only know that the only way to check.....

any detail guide for the SAM for using nvidia gpu??
what i read is need to configure the bios to enable SAM before installing window?
if the window installed is during bios did not enable SAM, it will not be booted up <-correct? 

What Platforms Support Resizable BAR?

GeForce RTX 30 Series laptops with both Intel and AMD CPUs will support Resizable BAR starting with their release in the coming weeks. Check with each laptop manufacturer about support on particular models.

For desktop systems to get the benefits of Resizable BAR, you will need a graphics card, motherboard and graphics driver that support the feature. New GeForce RTX graphics cards starting with the GeForce RTX 3060 will have support for Resizable BAR. NVIDIA and our GPU partners are also readying VBIOS updates for existing GeForce RTX 30 Series graphics cards starting in March.

Additionally, NVIDIA has been working closely with Intel, AMD and major motherboard manufacturers, including ASUS, ASRock, EVGA, GIGABYTE, and MSI, to bring Resizable BAR support to a wide range of motherboards.

“Intel has been working with NVIDIA to enable Resizable BAR, an advanced PCI-Express technology, across the PC ecosystem,” said Fredrik Hamberger, GM of Premium & Enthusiast Laptop Segments at Intel. “This feature can give gamers an extra boost in gameplay FPS on Intel’s new 11th generation H/S and select 10th generation systems when paired with supported graphics cards, including NVIDIA GeForce RTX 30 Series GPUs.”

Our Game Ready Driver with Resizable BAR support will be released alongside the GeForce RTX 3060 in late February.

Note: Don't bother. Need nvidia to release compatible vbios or some sort of loadable microcode (through drivers) before SAM can be used.

AGESA 1.2.0.0 doesn't seem to make any difference to my Infinity Fabric OC, still limited to 1866Mhz. 
Speaking of which, which batch is your 5900x?
My 5950x batch is 2046 = year 2020 week 46.