NVIDIA responded that: “The capability for resizable BAR is part of the PCI Express spec. NVIDIA hardware supports this functionality and will enable it on Ampere GPUs through future software updates. We have it working internally and are seeing similar performance results.” And indeed, it has been a part of the PCIe specification since 2008. This document dating to 2008 says that “This optional ECN adds a capability for Functions with BARs to report various options for sizes of their memory mapped resources that will operate properly. Also added is an ability for software to program the size to configure the BAR to.” Every PCIe compatible device can enable it with the driver update through the software.
AMD’s SAM implementation currently requires a Ryzen 5000 series CPU, 500 series motherboard chipset, and the latest Radeon RX 6000 series GPU. NVIDIA’s implementation could cover a wide range of hardware, including Intel and AMD CPUs and their respective platforms. That means that even the PCIe 3.0 standard will get some love, as the current Intel desktop platforms are limited to the PCIe 3.0. NVIDIA will use a driver update to enable such a feature, however, it may take some time to arrive as the feature is still being developed.