Is This AMD's Secret Weapon?

Is This AMD's Secret Weapon?
5 min read
06 January 2021

Are you in the market for a new graphics card? If so, you've probably seen plenty of performance reviews that primarily focus on the GPU itself. But the video memory of a graphics card can often be a bottleneck. And I'm not just talking about how much VRAM you have or how fast it is, but the way that the rest of your system talks to it.

This is an issue that AMD has tried to resolve with a new feature called Smart Access Memory. And to find out more about it we spoke with Nish Neelalojanan, I'm so sorry, the product manager for AMDs new Radeon RX 6000 Series GPUs.

So the particular bottleneck AMD was hoping to address was the data link between the graphics card's video memory, and the systems CPU. Is This AMD's Secret Weapon?The CPU needs to communicate regularly with the VRAM in order to ensure that the VRAM has the correct data for the GPU to act upon.

Historically, the CPU could only access 256 megabytes of VRAM at once. This limit was actually set long time ago, back when cards with one gigabyte or less of VRAM were far more common. But these days, the 256 Meg. limit, which has been kept in place in order to ensure compatibility with all their 32-bit CPUs is a real bottleneck that can result in tangible performance loss. Because of the space constraint created by this limit, data can get shunted over to your main system memory instead, which slows things down.

Smart Access Memory addresses this by taking advantage of a new feature, that's actually in the PCIE, or PCI Express standard called Resizable BAR. Is This AMD's Secret Weapon?This allows your CPU to access much more VRAM at once, multiple gigabytes in fact depending on how much VRAM you have on your card. AMD has built on the Resizable BAR feature with compatibility testing and driver optimizations that attempt to place resources the CPU needs to access frequently, such as render commands onto the VRAM instead of system memory.

Unsurprisingly however, the exact performance benefits will depend a lot on your workload and which game you're playing. Although AMD has tried to make their driver optimizations effective across a range of titles, developers also need to make use of the Resizable BAR feature. Is This AMD's Secret Weapon?AMD is claiming that Smart Access Memory boost performance by an average of 6% in terms of frame rate. But what do you need to take advantage of it and get that 6%?

Well,  the feature only works if you have a Ryzen 5000 CPU, a Radeon RX 6,000 GPU and a 500 series AMD chip set, the Holy Trinity. But hold on a second, it's based on Resizable BAR which is part of an open standard. Why do you need such a specific hardware combo? Well, there is not some kind of inherent technical limitation that you can only get around if you have those specific parts. AMD's approach is partly to promote their newest products, but they also want to do more validation and testing before Smart Access Memory is enabled on older equipment, which AMD does plan on doing in a phased rollout.

Team Red is also working with, believe it or not, Intel and Nvidia to enable similar technologies on those platforms. Ultimately AMDs vision is to have Smart Access Memory be similar to FreeSync. AMDs specific implementation would still be called Smart Access Memory but the underlying tech could be used by other companies.

This is especially good news if you want a CPU or a GPU that isn't from AMD. And Nvidia has already confirmed a similar feature for their own GPUs is in the works. But if and when you do get a system that supports Smart Access Memory, be sure to confirm that Resizable BAR support is turned on in your BIOS.Is This AMD's Secret Weapon? For now, it's actually off by default to try to prevent errors with hardware or software that doesn't support it fully.

So it seems like AMD's philosophy for now is better safe than sorry, which anyone who's ever fried a CPU can certainly appreciate. 

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Alex 9.8K
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