Nvidia is working on competing technology to AMD's Smart Access Memory for RTX 30 series...

nanoguy

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In brief: AMD touted a new Smart Access Memory feature for its RDNA 2 graphics cards (Radeon RX 6000 series) as something exclusive to an all-AMD configuration, but Nvidia says it will soon enable similar functionality for RTX 30 series Ampere GPUs that work will work when paired with either an AMD or Intel CPU.

When AMD launched its Radeon RX 6000 series graphics cards earlier this month, it was shown featuring double the performance of the previous generation (AMD's numbers, not ours, yet). The RDNA 2 architecture afforded those gains relying on three nifty tricks to achieve some of the purported performance claims: a 128 MB Infinity Cache, RAGE Mode, and Smart Access Memory.

Of those three, only Infinity Cache is a true AMD exclusive. RAGE Mode is essentially an overclocking profile in the Radeon Software, and its results may vary depending on the silicon lottery.

Smart Access Memory (SAM) as a performance-boosting technology is an interesting feature that AMD says will only work when pairing a Ryzen 5000 series CPU with a Radeon 6000 series graphics card on a 500 Series motherboard. Essentially, it allows dynamic expansion of the data channel between the CPU and the graphics memory (VRAM) to improve overall performance -- up to 11 percent according to AMD.

In a typical PC configuration today, only a small portion of the frame buffer (typically 256 MB) used by the GPU is exposed over the PCIe bus. Smart Access Memory is marketing speak for something called 'resizable base access register (BAR),' which is actually part of the PCIe 3.0 and later spec, and supported through the Windows Display Driver Model (WDDM) v2.

So far, AMD has created the perception that this technology was exclusive to its RDNA 2 graphics cards, but recently Nvidia told GamersNexus that its Ampere cards also support resizable BAR and achieve similar performance gains when they have it enabled. However, that will come through a future software update, with no indication as to when. AMD's RX 6000 series cards are set for release next week (reviews!!), which is a tight window for Nvidia if it wants to have the drivers ready by then.

Interestingly, Nvidia intends to make this work with both AMD and Intel CPUs and on either PCIe 4.0 or PCIe 3.0 motherboards, throwing the ball in AMD's court to do the same. This means AMD will likely be the first to support resizable BAR, but Nvidia may eventually have it working on many more configurations. And if it brings the same performance gains as it does for RDNA 2 cards to Ampere, it might change the picture we've seen in AMD's glossy benchmarks.

One way or another, it remains to be seen if you will be able to get ahold of a Ryzen 5000 CPU, RTX 3000 or Radeon RX 6000 graphics card before the year is over.

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HardReset

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Interestingly, Nvidia intends to make this work with both AMD and Intel CPUs and on either PCIe 4.0 or PCIe 3.0 motherboards, throwing the ball in AMD's court to do the same. This means AMD will likely be the first to support resizable BAR, but Nvidia may eventually have it working on many more configurations.
And? Where AMD has said Smart Access Memory is restricted to 500-series motherboards and Radeon 6000 cards only?

To make resizable BAR to work, support is needed (at least) from OS, video card, CPU, motherboard and BIOS.

So AMD only promises support for platform it can guarantee this technology work. Nvidia "promises" wider support, that is not any wider than AMD's because right now only 500-series motherboards are only one that have BIOS support for feature...

So if they had it all along since PCIe 3.0, why did wait to do something with it now? Would seem like an easy performance boost if you just need to enable it in software...
It came with PCIe 2.0 in fact.

You need BIOS support for it too. And that's why Nvidia's promises are nothing more than marketing BS.
 

HardReset

Posts: 839   +375
This PCIe 3.0 and 4.0 support is another thing.

AMD promised this technology is supported on Radeon 6000-series GPU AMD AMD 500-series motherboard. Both support PCIe 4.0.

So why AMD should promise support anything else than PCIe 4.0 with hardware that supports PCIe 4.0? Suddenly that's same that AMD only supports PCIe 4.0 and not 3.0. Sometimes I wonder how stupid people really are.

Smart Access Memory is marketing speak for something called 'resizable base access register (BAR),' which is actually part of the PCIe 3.0 and later spec, and supported through the Windows Display Driver Model (WDDM) v2.
PCie 2.1 spec in fact, source https://www.intel.com/content/dam/altera-www/global/en_US/uploads/e/e2/PCI_Express_Base_r2.1.pdf
 

Achaios

Posts: 61   +204
Thanks to AMD and Lisa Su, PC enthusiasts will get a free performance boost that NVIDIA would never have given us in the 1st place b/c they, like Chipzilla, are trying to sell to customers the least performant GPU for the most outrageous sum of money and with the least memory on board the can get away with.

 

emmzo

Posts: 256   +216
So, the famous RAGE mode turned out to be just an overclocking profile in the Radeon Software and SAM turns out to be another software trick and not something physically built into the hardware, as it is not exclusive to AMD CPUs. So much for the hype. We will see if AMD has a serious response to NVidia`s DLSS, because otherwise hmm...
 

Lionvibez

Posts: 2,053   +1,426
So, the famous RAGE mode turned out to be just an overclocking profile in the Radeon Software and SAM turns out to be another software trick and not something physically built into the hardware, as it is not exclusive to AMD CPUs. So much for the hype. We will see if AMD has a serious response to NVidia`s DLSS, because otherwise hmm...
They already said they did.

Were you not watching the RX 6000 preview event?

Do you always believe marketing from any of these companies?? I don't when its independently reviewed by a 3rd party then form an opinion.
 

emmzo

Posts: 256   +216
They already said they did.

Were you not watching the RX 6000 preview event?

Do you always believe marketing from any of these companies?? I don't when its independently reviewed by a 3rd party then form an opinion.
I see it now: they said they did, so it`s a given, but I should not believe marketing. Thank you, for your insight!...
 
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Great, that would make their 50k cards in the market (or so) run 1-2 % faster. So much investment but so little to sell.
We have made our amazing $700 card even faster. You should really really buy it. Oh darn, tough luck, there's nothing left. Nevermind, let's try to make it even faster.
 
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Irata

Posts: 991   +1,469
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I am curious how nVidia will support this via drivers if bios support is needed, as well ?

I also suppose that platform validation is needed in order to ensure that this works as intended.
 
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HardReset

Posts: 839   +375
I am curious how nVidia will support this via drivers if bios support is needed, as well ?

I also suppose that platform validation is needed in order to ensure that this works as intended.
They don't. What Nvidia says is that they offer support for any system with Ampere card.

What AMD says is that you'll need RX 6000 series card and 500 series motherboard.

Nvidia supports everything with right GPU, AMD does not. If your motherboard requires BIOS support with Nvidia card, it's not Nvidia's fault. It's motherboard makers fault. Bottom line: Nvidia >>> AMD 😆 :D"👏"
 

Puiu

Posts: 4,145   +2,789
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I see it now: they said they did, so it`s a given, but I should not believe marketing. Thank you, for your insight!...
What we know is that they are working on a solution that can compete with DLSS using MS's DirectML

It should be ok since that's what that tech is meant to be used for, but they are most likely at least 6 months out until they have something that works ok. If they manage to do it faster then good on them.

Here's a 2019 video that explains how it works (do keep in mind that what you'll see doesn't include any AI reconstruction or whatever AMD decides to include/change):
 
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emmzo

Posts: 256   +216
Famous? They listed it as one of several improvements. Honestly, if you're going to complain about something as minor as this you'll never be happy.
That`s the thing, it was not an improvement at all, just an OC software like Afterburner. And yes, silly me, I got hyped for some reason on that presentation, maybe because I genuinely wish AMD can fight back. So, I will be completely happy if that happens come Nov.18, but after these revelations, I got bummed.
 

neeyik

Posts: 1,459   +1,616
Staff member
I cannot see that there.

Currently only AMD products support this feature so obviously AMD cannot support something Nvidia or Intel does not support...
For Windows, AMD are definitely limiting to the Radeon RX 6000 series - check the footnote at the bottom. Linux has supported the function for a while I believe, as has AMD with their Linux drivers - just need to have a motherboard with the ‘Above 4G Decoding’ option in its BIOS enabled; it should then work with any AMD/Linux combination where everything is fully 64 bits.
 

HardReset

Posts: 839   +375
For Windows, AMD are definitely limiting to the Radeon RX 6000 series - check the footnote at the bottom. Linux has supported the function for a while I believe, as has AMD with their Linux drivers - just need to have a motherboard with the ‘Above 4G Decoding’ option in its BIOS enabled; it should then work with any AMD/Linux combination where everything is fully 64 bits.
No. Above 4G Decoding is requirement for SAM/BAR resize but it's not same thing at all. BIOS still need specific support for SAM/BAR resize. And currently only AMD 500-series boards and Radeon 6000 series cards have AGESA/BIOS that supports it, with or without Linux.
 

neeyik

Posts: 1,459   +1,616
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No. Above 4G Decoding is requirement for SAM/BAR resize but it's not same thing at all. BIOS still need specific support for SAM/BAR resize. And currently only AMD 500-series boards and Radeon 6000 series cards have AGESA/BIOS that supports it, with or without Linux.
While the Above 4G Decoding is indeed a requirement in order to resize the base address registers above the usual limit, and both require support in the BIOS, it also requires OS and driver support. Linux has supported it for a while, and AMD have enabled support for it for at least the Vega and Polaris architectures, but only in Linux drivers.

Edit: Here is a brief 2015 discussion between AMD and the developers of Linux Patchwork about properly accessing the ability to resize BARs:


The sticking point they were experiencing was BIOS/chipset support, not AMD’s GPUs. I wonder if AMD’s decision to support it with the 500 chipset and Big Navi only, with Windows, is because Microsoft are only offering support for it now, and only for limited hardware configurations.
 
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HardReset

Posts: 839   +375
While the Above 4G Decoding is indeed a requirement in order to resize the base address registers above the usual limit, and both require support in the BIOS, it also requires OS and driver support. Linux has supported it for a while, and AMD have enabled support for it for at least the Vega and Polaris architectures, but only in Linux drivers.
It is requirement but still it's not necessarily same thing. There have been dummy BIOS' that are supposed to support something but changing value actually does nothing. Also sometimes there are problems like this there setting should work but https://www.pugetsystems.com/labs/hpc/Will-your-motherboard-work-with-Intel-Xeon-Phi-490/

Linux has had support for it a while and it even seems Windows is supported but only with workstation class cards. It does seem Vega at least supports it too, right. Because it does seem to work with older cards with Windows also, then what's the problem supporting it generally? Unlike said on news, it seems to be supported for loooong time already.

This thing seems to be quite complicated. Why AMD only promises SAM to work with newest stuff while BAR address resize already work with other stuff too? Perhaps there is more than AMD told us. Perhaps SAM is something more than just renamed resizable BAR. Perhaps Zen3 and Radeon 6000 series have something custom.

Edit:

Edit: Here is a brief 2015 discussion between AMD and the developers of Linux Patchwork about properly accessing the ability to resize BARs:


The sticking point they were experiencing was BIOS/chipset support, not AMD’s GPUs. I wonder if AMD’s decision to support it with the 500 chipset and Big Navi only, with Windows, is because Microsoft are only offering support for it now, and only for limited hardware configurations.
Aside assumed custom stuff above, AMD said on event that it will work at launch "and run automatically on background". Something cannot be done with older hardware.
 
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