With the new Radeons and Ryzens, AMD has introduced Smart Access Memory technology, which uses a resizable BAR to streamline data transfer between computer memory and video card video memory. With the support of resizable BAR, other platforms and graphics cards have already started to be added. Let’s see what the resizable BAR will do with performance on Radeon and GeForce.
Some time after the introduction of Smart Access Memory, AMD’s designation for supporting resizable BAR technology on the PCI Express bus, only AMD AM4 with AMD 500 Series and 6000 Series Radeon chipsets supported the technology.
Nvidia and Intel joined us to work on reBAR support, so today, after updating the BIOS on motherboards and graphics cards, you can run reBAR on a number of other modern and previously unsupported products. For Intel, this means at least the LGA1200 platform, and for the Nvidia GeForce RTX 30 series.
Both Intel and Nvidia support reBAR for the mentioned products, because it cannot do without updating the firmware of the board and the graphics card, for specific products it depends on their manufacturer whether they have offered or will offer their support.
A beta version of the BIOS with reBAR support has appeared on the motherboard from our MSI MAG Z490 Tomahawk test kit quite a long time ago, currently there are even two sharp versions available that support reBAR. And it’s similar with most proven manufacturers.
To enable reBAR, you must load newer firmware and go to the advanced PCI Express bus settings, where you need to turn on Above 4G memory / Crypto Currency mining and Re-Size BAR Support.
Nvidia still in instructions for flashing older GeForce models for ReBAR support, he mentions that the Compatibility Support Module (CSM), which is often referred to as legacy, must be disabled in the BIOS, meaning that the board boots in UEFI mode and the system must boot from a GPT disk, not an old MBR.
For Nvidia, the functionality of reBAR can be verified in the control panel in the menu Help> System Information.
And you can easily tell this in GPU-Z, where since version 2.38.0 the Resizabe BAR item has been added at the bottom right, which shows either enabled or disabled if reBAR is not active.
ReBAR and games
For Radeons, the resizable BAR should work when turned on in the BIOS in all games. With the fact that when you turn it on, you run the risk that there will be no increase in performance, but on the contrary, its decline.
Nvidia took a different approach – on (politically incorrectly) whitelist she gave “proven” games, in which she activated resizable BAR using game profiles for drivers, with the addition of others will be added over time in future versions of drivers.
An optimist would say that she focused on the best and most popular modern AAA titles, a pessimist would say that the list looks like most methodologies for testing graphics cards.
|Games with Resizable BAR support on RTX 30 series graphics cards|
|list valid as of March 30, 2021|
|Assassin’s Creed Valhalla|
|Forza Horizon 4|
|Horizon Zero Dawn|
|Red Dead Redemption 2|
|Watch Dogs Legion|
These are the seventeen titles that the drivers supported with the official release of reBAR support for the GeForce 30 series desktop. I went google for a while and went through the release notes for several newer versions of drivers that Nvidia has released since then, but I haven’t registered that since more titles have been added.
We will test on two cards – reference AMD RX 6700 XT and GeForce RTX 3060 Vengus 12G OC from the last review. For Radeons, I’ve tested all the games, for GeForce only those that, according to Nvidia, currently have support for reBAR active.
AMD Radeon RX 6700 XT
MSI GeForce RTX 3060 Ventus 12G OC
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