UEFI Resizable Bar Mod enables support for ReBAR on old platforms
An ‘old machine savior’.
If you find yourself using an older platform that doesn’t support ReBAR, there’s a workaround available. A ReBarUEFI open-source project, highlighted by HKEPC and PCGamer, offers a solution that purportedly boosts gaming performance by an average of 6%.
ResizableBAR gained popularity in 2020 when AMD introduced its Smart Access Memory technology, which was basically a marketing name for an existing PCI Express feature that wasn’t commonly used. While the feature had been present in many motherboards for over a decade, it only gained widespread attention with AMD SAM, prompting other GPU vendors to follow suit.
The ReBarUEFI project operates as a boot-time module, replacing existing functions that check ReBAR compatibility. It adjusts the ReBAR size during system boot and cleverly convinces the system to activate it. Admittedly, this won’t be universally applicable, and some platforms might require enabling 4G encoding, even if such features are hidden in the options, but details on how to achieve it are available on the GitHub page.
Essentially, this modification allows users to activate ReBAR on aging platforms like the Intel Sandy Bridge from 2011. Despite the lack of support on many contemporary platforms when ReBAR became a recommended feature (and even a necessity for some GPUs), workarounds were available.
Once activated, ReBAR can allocate more than 256MB of system memory to be mapped to GPU memory. This allocation can noticeably enhance the performance of numerous games. According to the author of this mod, enabling ReBAR on a Core i3-3470 CPU paired with a Radeon RX 580 GPU could result in up to a 12% performance boost after activating 2GB of BAR size.
As always, when using mods, we encourage strong caution. Especially when tinkering with BIOSes.
Source: ReBarUEFI, PCGamer, HKEPC