MSI is preparing a new BIOS update to enable Re-Size BAR across all of its 400-series Intel motherboards. That now makes three major motherboard manufacturers, MSI and Asus, that are confirmed to be working on available beta BIOS updates to enable the functionality at the heart of AMD Smart Access Memory on Intel Z490, B460, and H410 motherboards.
Re-Size BAR isn't actually anything new, in theory. It's a part of the standard PCIe specification, although it was never really put to good use on a wide scale until AMD announced Smart Access Memory (SAM)—a new feature than allows Ryzen 5000 CPUs to access the complete VRAM of RX 6000-series graphics cards across 500-series motherboards.
And while the hot new feature on the block, in our testing of SAM we only experienced a marginal performance uplift across most games. It's great to switch on, if you have the option, but hardly something to go searching for as a must-have feature—especially as it might soon be available on a wider basis.
Shortly after SAM was announced, Nvidia claimed it had managed to get a similar functionality operating in the labs with its graphics cards. That's actually the pretty big caveat to today's motherboard support announcement—you'll still need an RX 6000-series graphics card to put it to good use right now, as no other GPUs currently support it, though Nvidia is expected to release an update early in the new year.
And good luck getting hold of one of those if you haven't already. The AMD RX 6800 XT and RX 6800 launched last month and sold out immediately. Your best bet will be to look out for stock of the RX 6900 XT on December 8, but we suspect this enthusiast-grade GPU to be even more sparsely found than the others.
Regardless, MSI aims to release Z490 motherboard BIOS support for Re-Size BAR this week and the complete B460 and H410 support by the end of the month.
Similarly, AGESA updates have effectively enabled the functionality on older X470 and B450 AM4 motherboards too, pending a BIOS update, although you'll still need to have other compatible hardware—CPU and GPU—in order to switch it on.
It's currently suggest that most recent Intel processors will be able to support the feature, while older AMD processors, pre-Ryzen 5000, may not have the prerequisite native instruction support (via CapFrameX). We cannot confirm or deny this at this time, however, so take that with a pinch of salt. It's also worth noting that AMD is so far the only company to extensively test all motherboards, GPUs, and CPUs of its latest generations with the function, and therefore we don't yet know how competitors' products will operate with Re-Size BAR enabled or the performance gain it will offer.
So there's still very little practical use to any of this, with so little hardware available, and very little to be gained in the end anyways. Still, free performance is free performance, however slight it might be.