alt Hacker NewsReBar's commercial name is AMD Smart Access Memory, it allows a PCIe device such as a GPU to map more VRAM to the system at once, which improves performance by reducing access overhead. This generated much fanfare in the early 2020s after AMD officially supported it in the newly released AMD Zen 3 CPUs with RX6800 series GPUs. It was marketed as a new technology to boost GPU/gaming performance. What AMD did was just rebranding an obscure feature in the PCIe specification [1]. As shown by this project, it was actually supported by the PCIe controller since Sandy Bridge, just disabled in the firmware. For a decade nobody bothered to use it. Presumably, AMD saw an opportunity and enabled it, presumably after validating the hardware and fixing any driver compatibility problems.
[1] This is nothing new in the tech industry. Intel rebrands DVFS as SpeedStep, IOMMU as VT-d, AMD rebrands the NX bit as Enhanced Virus Protection, etc.
Replies
IOMMU branding at least makes a little bit of sense. AMDs and Intels virtualisation ISA are completely different, including their IOMMU.
I feel part of the "Smart Access Memory" name is actually the driver features and paths to actually make use of it.
It's not like ReBar is a single toggle "Make Things Faster", but a different option in how it can map gpu memory to the cpu. The driver still needs to use it - and decide where it's use vs the "staging buffer" approach would actually be be benefitial.