arc-rebar enables Resizable BAR on old boards for Intel Arc GPUs

Developer Rod Burlamaqui released arc-rebar, a Linux tool that turns on Resizable BAR for Intel Arc GPUs on motherboards that never offered the option. It runs from initramfs before the GPU driver loads and leaves the BIOS, kernel and Intel drivers untouched. On a test system with a B580, CPU-visible VRAM grew from 256 MiB to a 16 GiB window, and measured bandwidth rose from 15 GB/s to 392 GB/s.

• The tool runs from initramfs at every boot before the GPU driver loads
• On a Supermicro X9DRH-7TF with a 2015 BIOS, a B580 went from 256 MiB to a 16 GiB window
• Measured VRAM bandwidth jumped from 15 GB/s to 392 GB/s
• A 4K Vulkan blur that used to stall ran at 39–50 FPS