Rod Burlamaqui's arc-rebar project patches a critical PCIe limitation: Intel Arc GPUs lose catastrophic bandwidth on motherboards without Resizable BAR support. On a 2015 Intel Xeon board paired with an Arc B580, bandwidth jumps from 15 GB/s to 392 GB/s, a 26x gain, by running a BAR configuration fix inside initramfs before the GPU driver ever loads. Requirements are narrow: Debian or Ubuntu, and a supported Intel Arc GPU.
The root cause is architectural. AMD and Nvidia built their GPU lineups in an era before ReBAR mattered, so their designs degrade gracefully without it. Intel Arc was engineered with ReBAR as a core dependency, not an optional feature. Without it, the system falls back to the PCIe default of mapping only 256 MB of VRAM into the host address space, instead of the full card. The motherboard never signals 64-bit BAR support during PCIe bus enumeration, and performance craters as a result.
The full project details on GitHub are worth reading for the initramfs hook implementation specifically, how Burlamaqui intercepts the boot sequence at exactly the right moment to reconfigure BAR allocation before the driver claims the device. If you run older Xeon workstation hardware and have avoided Arc cards because of compatibility concerns, this changes the calculus.
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