MSI announces Resizable BAR support for a host of its AMD and Intel processor motherboards

Following the announcement of Resizable BAR support on NVIDIA GeForce RTX 30-series graphics cards, MSI has rushed to announce the support across a range of its AMD and Intel processor-based motherboards. Surely the same boards will also support AMD Radeon RX 6000 series graphics cards.

The technology is implemented on most MSI motherboards with Intel Z590, B560, H510, Z490, B460, H410, Z390, H370, B360 and H310 chipsets and also on AMD motherboards with TRX40, X570, B550, A520, X470, B450 chipset. The company warns that on AMD motherboards the technology does not work with all processors for AM4 pads (at least on all Ryzen 5000). Of course, it is recommended to upgrade your motherboard to the latest firmware version and activate the appropriate items in the BIOS settings: Re-Size BAR and Above 4G Memory/Crypto Currency mining. MSI says that according to its tests the technology works great on all compatible platforms.

Resizable BAR technology is a part of PCI Express interface specification since v2.0 but AMD drew public attention to it only last autumn by introducing it as Smart Access Memory in its Radeon RX 6000 series graphics cards. With Resizable BAR, the CPU accesses the entire video memory array, while Windows PCs without this feature can access a maximum of 256 MB at a time. This eliminates I/O channel bottlenecks and, according to AMD, delivers up to a 10–15% performance gain in some games.

ASUS and MSI showed AMD Smart Access Memory on old AMD processors with Zen and Zen 2

At the announcement of Radeon RX 6000-series graphics cards, AMD noted the Smart Access Memory (SAM) technology, which provides an increase in performance when the gas pedal works with Ryzen 5000 (Zen 3) processors. Previously, it was reported that Ryzen 3000 and older AMD chips, unlike Intel processors, do not support SAM technology, due to lack of the necessary hardware and PDEP instructions support. But it turns out that not everything is that simple.

To begin with, SAM is based on the Resizable BAR (Base Address Registers) technology which is part of the PCI Express interface specifications since v2.0 and is not exclusive to AMD. Whereas a regular Windows based PC can only directly access up to 256MB of graphics memory, the Resizable BAR technology allows you to expand the data channel allowing the processor to access the entire video memory array at once. This eliminates potential bottlenecks and provides performance boost in some games (up to 15 % according to AMD estimates). This is especially true nowadays when the amount of video memory used in games often exceeds even 10 GB. Resizable BAR quite works on a bunch of Radeon RX 6000 and Intel processors on ASUS and ASRock boards. Since it is part of the PCI Express specifications, NVIDIA also plans to add support for this technology to some of its graphics gas pedals.

Rumors regarding the lack of SAM support in Ryzen 1000, 2000 and 3000 chips were first refuted by Ian Curtress of Anandtech, who got an explanation from AMD itself. It turns out that SAM does not rely on the PDEP instruction and will work regardless of how well the instruction is supported by the processor.

Now MSI and ASUS have demonstrated how SAM works on various AMD Ryzen processor series that do not have the Zen 3 architecture. According to the published screenshots, AMD Ryzen 4000G and Ryzen 3000 series processors with Zen 2 architecture will also support SAM on AMD 500 series chipset motherboards. ASUS, on the other hand, has shown the possibility of using Re-Size BAR with the Ryzen 7 1700 processor based on Zen. Earlier this week Igors’LAB published a story that NVIDIA is also working on an alternative to AMD SAM technology. It is claimed that there are discussions within the company as to whether the GeForce RTX 30xx series should support this technology. It's unclear if any final decisions have been made on this, but given that NVIDIA has said it's considering adding Resizeble BAR support, it would be too late to back out.

Meanwhile, AMD hasn't made any public statements regarding potential SAM support on older Radeon graphics gas pedals.

AMD has promised up to 15% performance improvement with Smart Access Memory

Yesterday AMD released its flagship Radeon RX 6900 XT graphics card based on RDNA 2 architecture. One of the advertised features of this and other Radeon RX 6000 series cards is AMD Smart Access Memory (SAM) technology. More and more motherboards of 400 and 500 series (for example, recently reported by Biostar) support this technology, and AMD decided to present a commercial about this technology.

AMD introduced the SAM technology during the announcement of the Radeon RX 6000 graphics cards and initially announced it only for the Ryzen 5000 processor. While conventional Windows-based PCs can only access up to 256MB of graphics memory at the same time, this technology allows the processor to extend the data channel, allowing the entire video memory array to be accessed at once, eliminating potential bottlenecks and achieving improved performance in some games. This is especially true now, when the amount of video memory used often exceeds 10 GB.

In this video, the company promises a noticeable performance increase in some games when activated SAM. For example, Forza Horizon 4 and Assassin's Creed Valhalla get a 1440p resolution gain on AMD Radeon RX 6900 XT up to 15 %, while Ashes of Singularity: Escalation in 4K shows a 13 % gain. The company still recommends using the technology on AMD 500 series motherboards with AMD Ryzen 5000 processors and AMD Radeon RX 6000 graphics cards. This requires the AMD Radeon Software Driver 20.11.2 or later, a motherboard with fresh firmware based on AMD AGESA 1.1.0.0 and activation of Above 4G Decoding and Re-Size BAR Support in the BIOS:

Recall: SAM is based on Resizable BAR (Base Address Registers) sizing technology, which is part of the PCI Express interface specifications since version 2.0 and is not an exclusive of AMD. SAM works quite well on Radeon RX 6000 and Intel processors on ASUS and ASRock boards, but AMD Ryzen 3000 and older processors do not support it hardware. Since this is part of the PCI Express specifications, NVIDIA also plans to add SAM support to some of its graphics gas pedals.

Ryzen 3000 and older AMD processors do not support AMD Smart Access Memory, but Intel does.

The situation with Resizable BAR (Base Address Registers) technology, which is part of the PCI Express interface specifications since version 2.0 and is the basis for AMD Smart Access Memory (SAM), continues to clarify. Recently we have written that SAM has worked on a bunch of Radeon RX 6000 and Intel processors, and now the details of older AMD processors are known.

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Recall: AMD introduced SAM technology during the announcement of Radeon RX 6000 graphics cards and initially announced it only for Ryzen 5000 processors. While in conventional Windows-based PCs, processors can only access up to 256MB of graphics memory at the same time, this technology can expand the data channel, allowing the processor to use the entire video memory array at once and remove potential bottlenecks, achieving improved performance in some games.

It seems that it is no coincidence that AMD started talking about SAM support only with the launch of Zen 3 architecture; the fact is that AMD Ryzen 3000 processors of Matisse family based on Zen 2, as well as older solutions based on Zen+ and Zen do not support this feature. It turned out that PCI-Express bus of Ryzen 5000 Vermeer processors includes PCIe physical layer functionality called full-rate _pdep_u32/64, which is required for Resizable BAR.

Official data on performance boost from SAM on AMD Ryzen 5000 and Radeon 6000 platforms

More interesting is that Intel processors have been supporting this functionality since the 4th generation of Haswell's Core, which added a 20-band PCI-Express Gen 3.0 bus. This means that every Intel processor released since 2014 is technically capable of supporting Resizable BAR, and the question is only for motherboard manufacturers that release UEFI firmware updates for their products (i.e. Intel 8th and later series chipsets).

AMD is widely marketing SAM as a means to increase performance by 1–2 % for Radeon RX 6800 series graphics cards. Since this is part of the PCI Express specifications, NVIDIA also plans to add support for it to some of its GPUs.

Tests have confirmed that AMD Smart Access Memory technology has worked on the Intel platform

Resizable BAR (Base Address Registers) technology is part of the PCI Express interface specifications since version 2.0 & ; it is the basis of AMD Smart Access Memory (SAM), but is no longer exclusive to owners of new Ryzen chips. Recently ASUS released firmware for motherboards with Intel Z490 chipset, which adds Resizable BAR support.

When this functionality is enabled in the BIOS of Intel Z490-based motherboards, ASUS AMD Radeon RX 6000 series graphics cards should automatically take advantage of this technology. AMD never said that SAM would be exclusive to Radeon RX 6000 and Ryzen 5000 processors. Only these products are listed as supported by AMD because AMD has conducted tests with them and is confident that they will work. Another reason is obviously marketing and a desire to increase sales of their own devices.

Japanese site ASCII decided to test the SAM in practice in the Intel platform. The site staff used a Core i9-10900K processor and a reference Radeon RX 6800 XT with and without active Resizable BAR function. As we already know, activation of SAM does not always give a noticeable performance gain even on a bunch of Ryzen 5000 and Radeon 6000 & ; everything depends on the specific game. That's why only those projects that have already proven SAM gains were included in the test: Assassin’s Creed Valhalla, Forza Horizon 4, Red Dead Redemption 2 and Rainbow Six Siege.

Official data on performance gain from SAM on AMD Ryzen 5000 and Radeon 6000 platforms.

So, on the Intel Z490 platform in Assassin’s Creed Valhalla at 1920 × 1080 and the highest quality, the activation of Resizable BAR gives both minimum and average frame rates increase: In Forza Horizon 4, at 2560 × 1440 and maximum quality settings, you'll feel the same gain (note that the graphics incorrectly specify resolution; 1920 × 1080): In Red Dead Redemption 2 at 1920 × 1080, the Resizable BAR increases the minimum frame rate multiple times to provide a smoother gaming experience: Finally, in Rainbow Six Siege at 1920 × 1080 at high quality settings and 100 %-scale rendering, the game shows an improvement in minimum frame rate and minimal increase in average performance: Recall: AMD introduced SAM technology during the announcement of Radeon RX 6000 graphics cards. While conventional Windows-based PCs can only access a portion of the graphics memory (VRAM) at the same time, this technology allows the processor to extend the data channel, allowing the entire video memory array to be used at once and eliminate potential bottlenecks, achieving improved performance in some games.