When AMD introduced its Smart Access Memory (SAM) technology, it was used as one of the key advertising points for its 5000 series of Ryzen processors based on Zen 3 architecture. At the time of launch, it was believed that only the latest generation of Ryzen processors can support it and only AMD GPUs can see a benefit in performance. However, later on, many of the motherboard makers have been playing with BIOS updates and have found a way to enable resizable BAR, the technology used for SAM, on non-AMD platforms. Today, thanks to the Reddit user Merich98 we have found out that ASUS has enabled resizable BAR support via BIOS update.

The user has used BIOS version 2409, released just a few days ago, on ASUS B450-PLUS motherboard. The feat is no extraordinary because it works on a B450 motherboard, it has been supported for a long time, but rather the feat is impressive because it works with the first generation AMD Ryzen 7 1700 processor. This contradicts the theory that SAM only needs 5000 series AMD Ryzen processors to run. However, the gains were not that great. On average, the average frame rate number has increased by a small +0.839%. This could be attributed to some margin of error, so it seems like SAM is not giving much performance uplift in this case.

ASRock has released a BIOS update for their Z490 Taichi motherboard which implements a Clever Access Memory (CAM) system (might I say that's as clever as it sounds?) CAM is basically ASRock's own marketing push based on AMD's SAM, which is in itself a marketing push based on PCIe's Resizable BAR feature (the amount of marketing names employed to describe the same set of features is becoming mind-boggling). The feature is available through the 1.72 BETA Bios for the Z490 Taichi motherboard, and WCCFTech ran some quick and dirty tests on a Z490-based system with an AMD Radeon RX 6800 XT graphics card to verify what (if any) performance differences arose.

The tests were done at 4K resolution for Shadows of the Tomb Raider and Assassin's Creed: Valhalla, running on an Intel Core i7-10700K processor and 2x 8 GB sticks of DDR4-2666 memory. The results? 3.32% performance improvement under Shadows of the Tomb Raider, and an impressive 11.54% improvement for Assassin's Creed: Valhalla (images to the left feature CAM on, and images on the right show CAM off). It seems it's only a matter of time until this amazing feature that's been available (yet untapped) for years now brings some very considerable and widespread performance improvements to users independent of platform. Kinda like finding a $10 bill in an old pair of jeans.

AMD Ryzen 3000 "Matisse" processors based on the "Zen 2" microarchitecture, as well as older AMD processors based on "Zen+" and "Zen" microarchitectures, do not support the company's Smart Access Memory (SAM) feature being introduced with Radeon RX 6000 series graphics cards. SAM is essentially a branding of the Resizable Base-Address Register (Resizable-BAR) feature developed by the PCI-SIG; which enables a processor to see a graphics card's entire video memory as a single addressable block, rather than through 256-megabyte apertures. Apparently the PCI-Express root complex of Ryzen 5000 "Vermeer" processors introduce an instruction called full-rate _pdep_u32/64, which is required for resizable-BAR to work.

It gets more interesting—Intel processors have been supporting this feature since the company's 4th Gen Core "Haswell," which introduced it with its 20-lane PCI-Express gen 3.0 root-complex. This means that every Intel processor dating back to 2014 can technically support Resizable-BAR, and it's just a matter of motherboard vendors releasing UEFI firmware updates for their products (i.e. Intel 8-series chipsets and later). AMD extensively advertises SAM as adding a 1-2% performance boost to Radeon RX 6800 series graphics cards. Since this is a PCI-SIG feature, NVIDIA plans to add support for it on some of its GPUs, too. Meanwhile, in addition to AMD 500-series chipsets, even certain Intel 400-series chipset motherboards started receiving Resizable BAR support through firmware updates.

AMD's recently-introduced SAM (Smart Access memory) feature enables users pairing an RX 6000 series graphics card with a Ryzen 5000 series CPU to take advantage of a long-lost PCIe feature in the form of its Resizable Bar. However, AMD currently only markets this technology for that particular component combination, even though the base technology isn't AMD's own, but is rather included in the PCIe specification. It's only a matter of time until NVIDIA enables the feature for its graphics cards, and there shouldn't be any technical problem on enabling it within Intel's platform as well. Now, we have results (coming from ASCII.jp) from an Intel Z490 motherboard (ASUS ROG Maximus XII EXTREME) with firmware 1002, from November 27th, paired with AMD's RX 6800 XT. And SAM does work independently of actual platform.

Paired with an Intel Core i9-10900K, AMD's RX 6800 XT shows performance increases across the board throughout the test games - which are games AMD themselves have confirmed SAM is working with. This means testing was done with Assassin's Creed Valhalla, Forza Horizon 4, Red Dead Redemption 2, and Rainbow Six Siege. The results speak for themselves (SAM results are the top ones in the charts). There are sometimes massive improvements in minimum framerates, considerable gains in average framerates, and almost no change in the maximum framerates reported for these games on this given system. Do note that the chart for Forza Horizon 4 has an error, and the tested resolution is actually 1440p, not 1080p.

When AMD introduced its Smart Access Memory technology, everyone was wondering will other GPU and CPU providers, namely Intel and NVIDIA, develop a similar solution to complement their offerings. The SAM technology is just AMD's way of naming PCIe resizable Base Address Register (BAR) technology, which has been present in PCI specifications for years as an optional feature. Why it's emerging now you might wonder. Well, the currently used PCIe revision has reached enough bandwidth on the bus to complement the complex data movement that GPU requires and now supports the use of the wider VRAM frame buffer.

It appears that not only AMD has this technology in its portfolio. ASUS has updated its BIOS firmware for its ROG Maximus XII Apex motherboard based on the Intel Z490 chipset, with some pretty interesting features. According to Tom's Hardware, we have information that the next release of BIOS firmware update 1003 for the ROG Maximus XII Apex motherboard will bring support for resizable BAR, making it a first on an Intel platform. For now, the beta 1002 BIOS supports it, however, a stable version will roll out in BIOS 1003. With the motherboard using PCIe 3.0 standard, a lower-bandwidth revision compared to AMD's platform, it will be interesting to see how resizable BAR is performing once the first tests come.

Update 09:45 am UTC: Chris Wefers, ASUS PR Germany, has announced that resizable BAR will be coming to all ASUS motherboards with Intel Z490/H470/B460 chipset, with alleged 13.37% performance increase in Forza Horizon 4, per ASUSes testing. You can see the test configuration in the image below.