Radeon Linux Drivers Now Only Officially Support Smart Access Memory On Zen 3 + RDNA2

[EduFrazao]

I have 5700 XT.
Experienced very low fps under Wine games on Linux, so I tested Unigine Superposition benchmark on Windows. Benchmark score 6000. Turned off Above 4GB Decoding in BIOS again, everything went back to normal = score 17400.
I installed Superposition on Linux as well.
Above 4GB Decoding=On and BAR=8192 = result 10000 in benchmark.
Above 4GB Decoding=Off and BAR=256 (default) = result 15300 in benchmark.

Mobo: Gigabyte model: AB350-Gaming 3-CF
UEFI: American Megatrends v: F51b date: 07/02/2020 (latest version)

OpenGL:renderer: AMD Radeon RX 5700 XT (NAVI10 DRM 3.40.0 5.10.2-2-MANJARO
LLVM 11.0.0)
v: 4.6 Mesa 20.3.1 direct render: Yes

So this is AMD drivers on Windows, and Mesa on Linux which needs to impove, or is it Gigabyte mobo BIOS? I understand what AMD said there is bugs and it will be disabled on my GPU by default, but I didn't anticipated 66% drop.

I Have the same results here. Only enabling BAR on BIOS cause many games to perform worse.. Mutch worse in fact. GTA V and World War Z shows 40% of performance LOSS. Some games, like Witcher 3 or Rage 2 was not affected.

The results does not change forcing sam to on or off using enviroment variables. I need to disable Above 4G decode and BAR in BIOS to get performance back to normal.

I've tested it with a 3700x and a 5900x on a Aorus Elite X570 with Agesa 1.2.0.0 BIOS and a RedDevil 5700XT.