Resizable BAR (Intel / NVIDIA ReBAR)

Resizable BAR (Base Address Register) is an optional PCIe specification feature allowing a PCIe endpoint (GPU) to advertise its full memory bar size to the host CPU, enabling the CPU to access the entire GPU VRAM in a single aperture rather than remapping a 256 MB window. Intel platforms from Z490 and 11th-gen Core support Resizable BAR (marketed as "Intel ReBAR"), requiring a BIOS update on older 10th-gen boards. NVIDIA RTX 30/40-series GPUs support ReBAR (released via driver+BIOS update for RTX 30, native on RTX 40). AMD platforms brand the same feature Smart Access Memory. Performance gains reach up to 15% in GPU workloads with frequent CPU-side texture streaming.