Open-source reBART driver enables Resizable BAR on Intel Haswell 8-series motherboards

Developer roschank has released reBART, an open-source UEFI driver that enables Resizable BAR support on Intel 8-series motherboards built for Haswell processors. The driver addresses a long-standing issue where Intel's platform code for the 8-series chipset generation skips mapping memory above 4 GB entirely, a gap that both the older 7-series and newer 9-series handle properly. Because every board manufacturer inherited this same firmware deficiency, the Above 4G Decoding toggle present in some BIOS interfaces was effectively non-functional.

The reBART driver operates by allowing normal boot progression and only activating immediately before the OS loader runs, at which point it relocates the GPU's memory aperture past the 4 GB boundary and redirects the boot display accordingly. Unlike the earlier ReBarUEFI project, reBART does not require module patching of existing firmware, though a DSDT patch remains necessary. Recent builds have added experimental support for Intel Arc discrete GPUs and multi-GPU configurations, with at least one user confirming both Arc A750 and Arc B580 cards functioning with unlimited BAR size on a Gigabyte GA-Z87M-D3H running Ubuntu.

How reBART works around the 8-series firmware gap

• Memory mapping fix: Intel's 8-series platform code omits mapping above 4 GB entirely, unlike 7-series and 9-series firmware; reBART shifts the GPU BAR window past this boundary at boot time.
• Late-stage activation: The driver hooks in right before OS handoff, preserving normal boot behavior including display output, then remaps the GPU aperture and redirects the framebuffer.
• Simpler integration: Unlike ReBarUEFI, reBART avoids module patching of existing UEFI firmware binaries, reducing modification complexity though a DSDT patch is still mandatory.
• Arc GPU support: Experimental builds add Intel Arc A-series and B-series compatibility, addressing Intel's prior guidance that Arc buyers without native ReBAR should use other vendors' hardware.
• Multi-GPU capability: Recent versions support multiple discrete GPUs simultaneously, with user validation on Gigabyte GA-Z87M-D3H under Ubuntu showing Arc A750 and B580 both operating with unlimited BAR size.

Why it matters

For Linux users maintaining aging but capable Haswell workstations, reBART unlocks measurable GPU performance improvements in Vulkan and DX12 titles through Proton without requiring full platform replacement. The project also demonstrates how open-source firmware tooling can correct vendor-abandoned hardware limitations, extending useful lifespans of systems that would otherwise contribute to e-waste streams. However, the need for BIOS flashing and DSDT patching carries real bricking risk, as evidenced by at least one failed ASUS Z87-Plus boot attempt.