I'm in the process of building a NAS, and went with the Asrock Rack x470D4U motherboard. I was unsure about it supporting re-bar. After tearing trough the BIOS, I was a bit annoyed when it was not supported. I ended up sending a mail to Asrock rack...
To my surprise they answered a day later with a BIOS update:
We add resized bar option in BIOS L4.27 Advanced -> PCI Subsystem Settings -> Re-Size BAR support.
The BIOS is not listed on Asrocks pages yet, so you should probably not use it yet. (Especially not since you got the file from a random guys blog).
But if somebody needs it, here's the file:
Other names for resizable bar:
- CAM - Clever Access Memory
- SAM - Smart Access Memory
- Rebar - Resizable bar