The PCI resizable-BAR feature is an absolute must for Intel Arc "Alchemist" graphics cards to perform as advertised, to the extent that Intel recommends sticking to "other vendors" (NVIDIA, AMD), for those on machines that lack resizable-BAR or prefer it disabled. In our testing of the Arc A380, we found a big performance gap between resizable-BAR being enabled and disabled. The company said that while it is working on driver optimizations that improve performance for machines lacking resizable-BAR, its general advice for those on older platforms is to stick with other vendors.

Resizable-BAR enables the software to see the entire video memory of a graphics card as a single large addressable block, rather than through 256 MB apertures. AMD and NVIDIA's driver architectures have optimized their memory-management to cope with these apertures through the advent of PCI-Express, but Intel Arc hasn't. Its memory-management model relies on large bursts of memory transfers, for which it needs resizable-BAR. The performance penalty for lacking it could be as high as 40 percent. In related news, Intel Graphics confirmed that the Arc A770 will be available both in 16 GB and 8 GB memory variants at launch—which is still slated for Soonuary, 2022.

NVIDIA's next-generation GeForce "Ada" graphics architecture may stick to PCI-Express 4.0 as its system bus interface, according to kopite7kimi, a reliable source with NVIDIA leaks. This is unlike Ada's sister-architecture for compute, "Hopper," which leverages PCI-Express 5.0 in its AIC form-factor cards, for its shared memory pools and other resource-sharing features similar to CXL. This would make Ada the second graphics architecture from NVIDIA to use PCIe Gen 4, after the current-gen "Ampere." The previous-gen "Turing" used PCIe Gen 3. PCI-Express 4.0 x16 offers 32 GB/s per-direction bandwidth, and NVIDIA has implemented the Resizable-BAR feature with "Ampere," which lets the system see the entire dedicated video memory as one addressable block, rather than through tiny 256 MB apertures.

Despite using PCI-Express 4.0 for its host interface, GeForce "Ada" graphics cards are expected to extensively use the ATX 3.0 spec 16-pin power connector that the company debuted with the RTX 3090 Ti, particularly with higher-end GPUs that have typical board power above 225 W. The 16-pin connector is being marketed as a "PCIe Gen 5" generation standard, particularly by PSU manufacturers cashing in on early-adopter demand. All eyes are now on AMD's RDNA3 graphics architecture, on whether it's first to market with PCI-Express Gen 5, the way RDNA (RX 5000 series) was with PCIe Gen 4. The decision to stick with PCIe Gen 4 is particularly interesting given that Microsoft DirectStorage may gain use in the coming years, something that is expected to strain the system bus for the GPU, as SSD I/O transfer-rates increase with M.2 PCIe Gen 5 SSDs.

MSI announced that it is bringing the PCI-SIG resizable base-address register (resizable BAR) support to a variety of older PC platforms, and not just the latest Intel 400-series and AMD 500-series. Among these are Intel 300-series, AMD 400-series, and AMD TRX40. This should come as a boon to those with 8th Gen and 9th Gen Core "Coffeee Lake" processors, such as the i9-9900K and i5-8400. Support is also being added to AMD X470 and AMD B450 chipset motherboards, however, this requires a compatible processor, and the latest beta UEFI firmware that supports them. Lastly, resizable-BAR support is making its way to the AMD TRX40 chipset (Socket sTRX4) Threadripper platform.

Resizable BAR is a feature that allows a processor to see the entire video memory of a discrete GPU as a single addressable block, rather than through 256 MB apertures. This has the potential to tangibly improve performance with certain games. Currently, AMD's Radeon RX 6000 series "Big Navi" GPUs; and NVIDIA's GeForce RTX 30-series "Ampere" GPUs support it. MSI is releasing UEFI firmware updates that add resizable-BAR support. Keep checking the "support" section of your motherboard's product page on the MSI website.

NVIDIA on Tuesday announced a roll-out of its implementation of the PCI-SIG resizable base-address register (BAR) feature to select GeForce products. The feature enables your CPU to see the entire video memory of your graphics card as one addressable block, rather than through 256 MB apertures. This should improve certain kinds of 3D rendering workloads, and game engines that are optimized to use it should see a tangible performance boost. AMD earlier introduced the exact same feature under its marketing name "Smart Access Memory," with its Radeon RX 6000 series.

NVIDIA announced that resizable-BAR support will be made available to GeForce RTX 30-series "Ampere" desktop graphics cards, notebooks that have RTX 30-series "Ampere" mobile GPUs, and future products. The support requires not just a compatible graphics card, but also a motherboard that supports the feature. Most leading motherboard- and OEM desktop manufacturers began rolling out resizable-BAR support through UEFI firmware updates. Using the feature requires you to run your machine in native UEFI mode (with CSM disabled).