PCIe Resizable BAR Expands CPU-Visible Device Memory Windows

Thu, 17 Sep 2026 00:00:00 +0700

A PCI Express device can expose memory and registers through Base Address Registers, usually shortened to BARs. The platform assigns address ranges to those BARs, and the CPU can then reach the mapped device resources through normal memory-addressed transactions.

For devices with large local memory, a small BAR can expose only part of that memory at once. Software may need to change which portion is visible through the aperture as access moves across the device’s memory. PCIe Resizable BAR adds a standard mechanism for selecting a larger supported BAR size, so a much broader region can remain CPU-visible at the same time.

Resizable BAR on Nalar

PCIe Resizable BAR Expands CPU-Visible Device Memory Windows