As you may already know GPU-Z software is the most popular graphics subsystem information and monitoring utility. TechPowerUp website recently released a new updated version 2.38.0 of this GPU monitoring utility which adds support for the Resizable BAR feature.
GPU-Z will now be able to tell whether Resizable BAR is supported, and if so, whether it is enabled or not. The latest version 2.38.0 also adds support for the following unannounced AMD Navi GPUs, RX 6700, RX 6600 XT, RX 6600, respectively, which confirms that we can expect all these Navi cards to be released soon.
Adding support for the above unreleased AMD GPUs confirms that the above rumored AMD Navi SKUs are on track, and we can expect these cards to hit retail shelves in future, hopefully. Most of the popular software utilities usually get an early update before the release of any product in the market.
And in this case the GPU-Z tool adds support for new and upcoming GPUs. The GPU-Z tool will also report the Resizable BAR info in the main tab, which means we can easily verify whether this feature is supported on the GPU and the said system/PC.
We already know AMD has officially announced its latest RDNA2 graphics card, the AMD Radeon RX 6700 XT. According to the red team, this new GPU will release on March 18th, will have a $479 MSRP, and will be available from both AMD and AIBs. However, there was no mention of the non-XT variant, the plain RX 6700 SKU, which GPU-Z’s updated log has just confirmed.
We also never got any concrete evidence/proof regarding the following rumored Navi cards as well, notably the RX 6600 XT, RX 6600, respectively.
This is the GPU-Z’s latest change-log, coming via TechPowerUp:
- Fixed BIOS saving on AMD RDNA2 cards. BIOSes saved with old GPU-Z versions are only 512 KB and will brick your card when flashed
- PCI-Express Resizable BAR status is now displayed in the main window
- Added support for negative temperature monitoring on NVIDIA
- Added support for AMD Radeon RX 6700 XT, RX 6700, RX 6600 XT, RX 6600, Lucienne APU integrated graphics
- Added support for NVIDIA GeForce RTX 3070 Mobile
AMD refers to Resizable BAR as “Smart Access Memory/SAM” instead. Resizable BAR is a tech via which assets can be requested as-needed and accessed. As such, the CPU will efficiently access the entire frame buffer. Moreover, transfers can occur concurrently, rather than queuing, whenever there are multiple requests.
AMD has already showcased this tech in action, showing an 8-15% performance boost in some games. This is free performance boost, without any image degradation/loss. Smart Access Memory feature will boost the overall gaming performance by optimizing the data transfer between the CPU and the GPU.
But unlike AMD, NVIDIA has actually extended support for this Resizable BAR tech on even PCIe gen 3.0 platforms. Which means Intel’s 10th gen core CPU lineup, and the respective 400-series chipset motherboards now also offer support for this feature.
It is typical today for a discrete graphics processing unit (GPU) to have only a small portion of its frame buffer exposed over the PCI bus. For compatibility with 32bit OSes, discrete GPUs typically claim a 256MB I/O region for their frame buffers and this is how typical firmware configures them.
A GPU, supporting resizable BAR, must ensure that it can keep the display up and showing a static image during the reprogramming of the BAR.
This feature is rather important for graphics hardware, because the PCI BARs are usually limited to 256MB while on modern cards you can easily find 4GB or more VRAM. The end result is that only a fraction of that VRAM is CPU accessible, causing a whole bunch of workarounds in the driver stack for that hardware.
AMD says that with SAM they can access all of the GPU memory, thus removing any bottlenecks. This will also allow for faster performance. In conventional Windows-based PC systems, processors can only access a fraction of graphics memory (VRAM) at once, limiting system performance.
With AMD Smart Access Memory, the data channel gets expanded to harness the full potential of GPU memory, utilizing the bandwidth of PCI Express to remove the bottlenecks and increase performance.
As of February 25th, 2021, Nvidia has enabled Resizable BAR support on the following PC titles, with more games to be added later on as the team does the internal testing:
- Assassin’s Creed Valhalla
- Battlefield V
- Borderlands 3
- Forza Horizon 4
- Gears 5
- Metro Exodus
- Red Dead Redemption 2
- Watch Dogs: Legion
As per Nvidia’s recent press release statement, as of February 25th, 2021, the following CPU chipsets and CPUs support Resizable BAR on GeForce RTX 30 series desktop GPUs.
Back in November 2020, in a recent statement to GamersNexus NVIDIA already confirmed that they are also working on their own SAM or the Smart Access Memory feature similar to what AMD has enabled on their RDNA 2 GPU lineup.
Resizable BAR is actually a part of the PCI-Express specifications, and NVIDIA’s existing hardware fully supports this functionality. NVIDIA has stated this SAM feature is going to be enabled through future GPU driver and software updates, and it will be compatible with both AMD and Intel processors.
BAR basically defines how much discrete GPU memory space can be mapped. Modern PCs are typically limited to 256 MB of mapped memory.
For enabling the Resizable BAR feature on any GeForce RTX 30 series GPU, after having updated your motherboard’s firmware/BIOS, you’ll need to update your GPU, and download the latest Nvidia game ready driver.
The GeForce RTX 3060 desktop graphics cards launched on February 25th, 2021, come with a pre-installed Resizable BAR-ready VBIOS. If you purchase one, all you need is a compatible motherboard and motherboard SBIOS, and the latest game ready driver.
Later on in March 2021, NVIDIA will release downloadable VBIOS updates for all Founders Edition GeForce RTX 30 series GPUs to enable Resizable BAR, and likewise, partners will release VBIOS updates for their custom models, too.
In practice, the performance benefits of Resizable BAR can vary substantially from game to game. According to NVIDIA’s testing, some titles benefit from a few percent, up to 10%.
However, there are also titles that see a decrease in performance, so NVIDIA will be pre-testing titles and using game profiles to enable Resizable BAR only in games where it has a positive performance impact.
That way you won’t have to worry about bugs or performance decreases, and won’t have to rely on the community to benchmark each title and discover whether Resizable BAR is beneficial in the games you’re playing.
As per this 2008 PDF document, “This optional ECN adds a capability for Functions with BARs to report various options for sizes of their memory mapped resources that will operate properly. Also added is an ability for software to program the size to configure the BAR to.”
This new technology feature will not require a PCIe Gen 4-compatible platform as it will be supported by PCIe Gen 3 systems as well.
Stay tuned for more tech news!