Resizable BAR on Intel CPUs – Performance Impact Tested
Resizable BAR support is now available on systems with Intel processors, arriving through new BIOS updates from motherboard vendors. With this, AMD’s “Smart Access Memory” has lost its AMD exclusivity, allowing the benefits of this technology to be enjoyed by a broader range of PC gamers.
Today, we will be looking at how Resizable BAR supports alters a gaming PC’s performance hen using Intel’s i9-10850K processors and AMD’s Radeon RX 6800 graphics card. This support comes via the latest BIOS for Gigabyte’s Z490 Aorus PRO AX motherboard.
Will Resiable BAR support deliver us higher framerates on an Intel-powered system? That’s what we are here to find out.
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Smart Access Memory – From AMD-only to almost everyone in 5 months
In October 2020, AMD announced Smart Access Memory as an AMD-only feature, arriving with Radeon 6000 series GPUs and Ryzen 5000 series processors. Now, it has become clear that Smart Access Memory will not be an AMD-only technology for long, as even now Intel has enabled the feature on their latest motherboard platforms, and Nvidia won’t be far behind.
Credit where credit is due, AMD were the first to enable PCIe’s optional resizable BAR feature with their Radeon RX 6000 series of GPUs. Doing so required major alterations to AMD’s Radeon GPU drivers, platform updates for 500-series and 400-series AM4 motherboards and redesigned BIOS’ on their Radeon RX 6000 series graphics cards. Only AMD could make that happen without the co-operation of 3rd parties.
AMD saw the benefits of PCIe Resizable BAR support and did that they needed to do to enable it on their Ryzen processors and Radeon graphics cards. In doing so, they created an ecosystem where their competitors could enable the feature on their platforms. Nvidia graphics cards cannot support PCIe Resizable BAR without compatible motherboards, and Intel platforms cannot utilise the feature without compatible graphics cards.
Intel platforms now have BIOS support for Resizable BAR on their Z490 platform, allowing users of Radeon RX 6000 series GPUs to access the benefits of AMD’s Smart Access Memory technology when using compatible Intel CPUs. Nvidia also plans to support PCIe Resizable BAR after they launch their RTX 3060 graphics card. Resizable BAR support is coming to all RTX 30 series graphics cards.
What is Smart Access Memory?
Before now, CPUs had access to 256MB of GPU memory, an allocation size which made a lot of sense in the early 2000s. Since then, GPU memory sizes have exploded, with AMD’s Radeon high-end RX 6000 series of graphics cards featuring a whopping 16GB of GDDR6 memory.
With AMD’s Smart Memory Access technology, AMD is granting their CPUs access to the entirety of the RX 6000 series’ frame buffer. Thanks to this access, AMD users can benefit from increased game performance within existing titles, and developers can exploit this access for further performance gains with future game releases.
This technology will allow CPUs and graphics cards to benefit from the bandwidth offered through PCIe 4.0, as increased GPU memory access will undoubtedly result in increased bandwidth utilisation. That said, it may take a while for PCIe bandwidth to become a limiting factor with some games.
Resizable BAR – Smart Access Memory for Everyone!
While AMD was the first to deliver Resizable BAR support on their Radeon RX 6000 series GPUs and Ryzen 5000 series processors, it hasn’t taken long for their competitors to catch up. This highlights how beneficial Smart Access Memory can be on PC, and how eager AMD’s rivals are to gain these same benefits on their hardware.
Enabling Resizable BAR Support
To enable Resizable BAR with our Intel i9-10850K and our Z490 Aorus PRO AX motherboard, we first updated our BIOS to Gigabyte’s latest version (F20a for this article). After that, we navigated to the Settings section of Gigabyte’s UEFI and then enabled “Above 4G Decoding”. Enabling this makes the Z490 Aorus PRO AX’s Resizable BAR option reveal itself.
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Once “Above 4G Decoding” is enabled, an option called Re-Size BAR Support will become available. Set this option to auto, and this will allow the feature to work on compatible graphics hardware.
Note that Resizable BAR support will only work if your motherboard, graphics card and GPU drivers all support Resizable BAR.
Assassin’s Creed Valhalla
Like our original AMD testing for Smart Access Memory/Resizable BAR, enabling Resizable BAR on an Intel-powered system has a transformative effect on Assassin’s Creed Valhalla. 1st percentile, average and maximum framerates are all boosted, so much so that our Resizable BAR results at 1440p are very close to our standard (Resizable BAR disabled) 1080p results.
It is clear from this result that Resizable BAR support can benefit Intel-powered systems, which is great for systems like our i9-10850K test system.
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Cyberpunk 2077
In Cyberpunk 2077, Resizable BAR support had a much smaller impact than it did with Assassin’s Creed Valhalla, though it nonetheless resulted in a notable boost our framerates at 4K, 1440p and 1080p.
These framerate gains are similar to our original Ryzen testing, which means that Resizable BAR is just as effective on Intel systems as it is on AMD.
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Forza Horizon 4
Like our original Resizable BAR testing, Forza Horizon 4 continues to be one of the games which see the largest performance benefits from Resizable BAR’s boosted memory access.
In Forza Horizon 4, Resizable BAR support allows our system to run better at 1440p than the game originally ran at 1080p, an impressive result to say the least. Our framerates are actually higher than what we saw with our AMD-based Ryzen 9 3950X system when Resizable BAR s enabled, as Forza appears to prefer our Intel i9-10850K processor.
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Horizon Zero Dawn
For Horizon Zero Dawn, we found that Resizable BAR had a little to no impact on the game’s performance. In our custom test scene, Resizable BAR support offers gamers no real performance benefits.
Resident Evil 3
With Resident Evil 3, we found that Resizable BAR support delivers us a notable boost in-game performance, especially at 1080p and 1440p. The framerate increase offered by Resizable BAR gets lower as Resident Evil 3’s resolution increased, though notable gains can still be seen at 4K.
Resizable BAR support should come as great news for those who want to play Resident Evil 3 on high refresh rate 1080p or 1440p displays.
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The Witcher 3: The Wild Hunt
In The Witcher 3, Resizable BAR support gives us a minimal increase in game performance. That said, the performance difference is so marginal that you wouldn’t notice the change in-game.
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Conclusion – Resizable BAR is coming to all of the latest PC hardware
Resizable BAR support has the potential to have a transformative impact on PC gaming, giving developers more freedom by granting them free access to GPU memory for CPU/GPU related tasks. AMD was the first company to deliver this, and soon all of their competitors will too.
Smart Access Memory is AMD’s brand name for Resizable BAR support, and while AMD was first, Intel was not far behind. It did not take long for Resizable BAR support to arrive on Z490, which allowed us to do our testing today with Intel’s i9-10850K processor.
Right now, all major motherboard manufacturers have updated their Z490 motherboards with Resizable BAR support. Furthermore, Resizable BAR will be supported on all of Intel’s Z590 motherboards. Intel has embraced the PCIe spec’s optional Resizable BAR feature, as they know how much it could impact the performance of future games.
Our results from Assassin’s Creed Valhalla and Forza Horizon 4 have already shown us that Resizable BAR support can deliver tremendous performance gains in existing games. Future titles have the potential to use Resizable BAR support more explicitly to deliver even larger performance benefits. AMD and Intel support this resizable BAR in their latest motherboard BIOS’. AMD supports it in their latest graphics cards, and Nvidia will be rolling out support for the feature in their future graphics cards drivers. Soon, Resizable BAR will be a feature that developers cannot ignore.
It is worth noting that the Resizable BAR support has delivered us similar performance gains on our Ryzen 9 3950X and Intel i9-10850K, highlighting that the Resizable BAR support does not deliver any additional performance benefits when used in conjunction with PCIe 4.0. This is great news for Intel Z490 motherboard users with 10th Generation CPUs, as they will not need a PCIe 4.0 platform upgrade to access the full benefits of resizable BAR support.
While large performance gains are possible through Resizable BAR support, this feature is not a magic bullet that will deliver you performance gains in all PC titles. Resizable BAR is designed to give your PC access to more resources, and from there it is up to your software to utilise those resources.
Only time will tell how Resizable BAR support will change PC gaming. Having Intel and Nvidia quickly follow AMD’s lead is a good sign of things to come, though it will likely take years for developers to utilise the feature to its fullest extent.