Developer Rod Burlamaqui has introduced arc-rebar, a Linux utility designed to enable Resizable BAR support for Intel Arc GPUs on motherboards that lack native firmware options. The tool operates during the boot process from initramfs, specifically targeting the PCIe switch integrated into Arc graphics cards.
Unlike previous solutions such as ReBarUEFI, this utility does not require modifications to the motherboard BIOS, kernel, or Intel drivers. It functions by writing to the GPU's ReBAR register and performing a rescan of the root port to bypass limitations imposed by small upstream BAR configurations.
Testing on a Supermicro X9DRH-7TF motherboard with a 2015 BIOS and dual Xeon E5-2670 v2 processors demonstrated significant performance gains. The CPU-visible VRAM window for an Intel B580 card expanded from 256 MiB to 16 GiB, covering the entire 12 GB capacity.
Performance metrics showed a substantial increase in VRAM bandwidth, rising from 15 GB/s to 392 GB/s. Furthermore, a 4K Vulkan blur task, which previously experienced stalls, achieved a frame rate between 39 and 50 FPS following the implementation of the tool.
