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

neeyik

Posts: 1,839   +2,151
Staff member
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.
It’s quite possible SAM is a little more than just resizable BAR support; we’re still waiting for AMD’s whitepapers, which isn’t helping with writing our forthcoming articles on it all!

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.
I’m pretty certain that they’re solely referring to Windows systems only. AMD are also being quite specific with their wording - in that footnote in their SAM webpage, they state that only Radeon RX 6000 series cards are validated. This suggests that they could potentially offer it in older hardware but since so much of rBAR depends on chipset/BIOS supporting it fully too, I can see why they just wanted it for the 500 series chips, with 6000 cards - it’s a far smaller number of configurations to test and validate.

Interestingly, rBAR has been available in Windows since WDDM 2.0 came out with Windows 10. Which all begs the question: ‘why now?’ AMD’s GPUs have supported since 2015, Linux and Windows have supported it for a number of years too. The PCIe controller must support it too but since the 500 chipset supports Zen+ CPUs onwards (X570, at least) then they’ve had support for it the controller for a number of years too.

In other words, there’s no immediately obvious reason as to why it has to be the 500+6000 combination. It seems to me that AMD have kept it aside for Big Navi to provide the ‘free’ extra % performance at 4K to throughly compete against or beat Ampere - the first Navi wasn’t powerful enough to compete against the 2080 Ti and the older GCN architecture was more limited by shader utilisation and internal bandwidth than external data restrictions.
 

HardReset

Posts: 1,070   +660
It’s quite possible SAM is a little more than just resizable BAR support; we’re still waiting for AMD’s whitepapers, which isn’t helping with writing our forthcoming articles on it all!

Yeah, good luck with that.

I’m pretty certain that they’re solely referring to Windows systems only. AMD are also being quite specific with their wording - in that footnote in their SAM webpage, they state that only Radeon RX 6000 series cards are validated. This suggests that they could potentially offer it in older hardware but since so much of rBAR depends on chipset/BIOS supporting it fully too, I can see why they just wanted it for the 500 series chips, with 6000 cards - it’s a far smaller number of configurations to test and validate.

Interestingly, rBAR has been available in Windows since WDDM 2.0 came out with Windows 10. Which all begs the question: ‘why now?’ AMD’s GPUs have supported since 2015, Linux and Windows have supported it for a number of years too. The PCIe controller must support it too but since the 500 chipset supports Zen+ CPUs onwards (X570, at least) then they’ve had support for it the controller for a number of years too.

In other words, there’s no immediately obvious reason as to why it has to be the 500+6000 combination. It seems to me that AMD have kept it aside for Big Navi to provide the ‘free’ extra % performance at 4K to throughly compete against or beat Ampere - the first Navi wasn’t powerful enough to compete against the 2080 Ti and the older GCN architecture was more limited by shader utilisation and internal bandwidth than external data restrictions.

That is one possible case, there are many others. Like SAM is only for Infinite cache chips (Radeon 6000-series), Zen3 have something custom Zen2 and earlier don't have etc.

AMD also said Ryzen 5000 CPU is needed so it may be CPU issue too. Or perhaps AMD just wants it to be PCIe 4.0 only at this time. There are just too many questions.

Main question is why Nvidia does not have this ready on pocket. Free 5-10% more performance and Nvidia seemed to think about this just after AMD's presentation. For AMD it's understandable since older cards were not even near enough fast. But Nvidia, they should have had this technology ready in case AMD gets something competitive. Now Nvidia is just doing damage control since AMD will got 12 year old tech on market before them...
 

treetops

Posts: 3,064   +784
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...
Check out turbo mode!
 

neeyik

Posts: 1,839   +2,151
Staff member
AMD also said Ryzen 5000 CPU is needed so it may be CPU issue too. Or perhaps AMD just wants it to be PCIe 4.0 only at this time.
I suspect it's more about PCIe 4.0 than anything else. Giving the CPU full access to the GPU's local memory across a 15.8 GB/s interface (I.e. PCIe 3.0) is equivalent to using single channel DDR4-2000 memory system, just in terms of bandwidth. At least with PCIe 4.0, that becomes 31.5 GB/s, which is DDR4-3900-esque.

Main question is why Nvidia does not have this ready on pocket. Free 5-10% more performance and Nvidia seemed to think about this just after AMD's presentation. For AMD it's understandable since older cards were not even near enough fast.
A 5 to 11% increase at 4K is indeed nothing to be sniffed at, but AMD have the advantage of just offering for it for a specific combination of their CPUs, chipset, and graphics card - something Nvidia can't do.

Well, they could be just as specific, but since Intel don't have a PCIe 4.0 CPU on the market at the moment, they're stuck with just offering it for AMD systems. The question for them is do they try to offer it for as many as a Ryzen combination as possible, or is it only going to be for PCIe 4.0 AMD setups too - if it is the case, then Nvidia potentially have a lot of face to lose, if their SAM implementation turns out to be worse or no better than AMD's.
 

HardReset

Posts: 1,070   +660
I suspect it's more about PCIe 4.0 than anything else. Giving the CPU full access to the GPU's local memory across a 15.8 GB/s interface (I.e. PCIe 3.0) is equivalent to using single channel DDR4-2000 memory system, just in terms of bandwidth. At least with PCIe 4.0, that becomes 31.5 GB/s, which is DDR4-3900-esque.

Latencies are bigger problem IMO. PCIe latency vs video card local memory latency is very big. Just speculation without knowing if that extra bandwidth is really needed. Or perhaps that extra bandwidth needed if SAM increase latency too if when pushing PCIe bus near limits.

A 5 to 11% increase at 4K is indeed nothing to be sniffed at, but AMD have the advantage of just offering for it for a specific combination of their CPUs, chipset, and graphics card - something Nvidia can't do.

Well, they could be just as specific, but since Intel don't have a PCIe 4.0 CPU on the market at the moment, they're stuck with just offering it for AMD systems. The question for them is do they try to offer it for as many as a Ryzen combination as possible, or is it only going to be for PCIe 4.0 AMD setups too - if it is the case, then Nvidia potentially have a lot of face to lose, if their SAM implementation turns out to be worse or no better than AMD's.

Or just marketing issue. AMD promises something and they are confident they can deliver with certain hardware. If AMD promises 5-10% with SAM using Radeon 6000-card, many people will cry when that 5-10% figure is much less when using other than 500-series chipset (=no PCIe 4.0). They could later enable it on other platforms, that time not promising 5-10% but just "something".

Nvidia could always say they just make video cards. Generally disadvantage for them but in this case also some advantage since they can always blame someone else (motherboard, CPU etc). AMD trying to offer full package must be much more careful.
 

Bamda

Posts: 231   +112
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...
Rage mode is not a overclocking profile! Learn something before you speak!
 

Bamda

Posts: 231   +112
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"👏"
Sure, I want to buy a over-hyped, lower specs and lower performing, hotter Graphic Card, LOL
 

Bamda

Posts: 231   +112
Why is NVIDIA now coming out with this, because AMD did! Plus until I see benchmarks I won't believe anything from NVIDIA! That looks like marketing BS! Too much-underhanded BS coming from NVIDIA for too long! I have lost so much respect for NVIDIA, trust is earned they have not shown to be an untrustworthy company.
 

emmzo

Posts: 280   +247
Rage mode is not a overclocking profile! Learn something before you speak!
It`s advertised now by AMD themselves as "one-click overclocking". You go to Performance > Tuning via Radeon Software and Preset to activate it. Idk how that is "one-click", maybe they have shortcuts. Other profiles include Quiet and Balanced. Sorry to burst your bubble.
 
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Bamda

Posts: 231   +112
It`s advertised now by AMD themselves as "one-click overclocking". You go to Performance > Tuning via Radeon Software and Preset to activate it. Idk how that is "one-click", maybe they have shortcuts. Other profiles include Quiet and Balanced. Sorry to burst your bubble.
Again learn before you speak!

It turns out that AMD Rage Mode is not a genuine overclocking feature. Instead, the company likened it to a user profile. AMD officially categorizes it as a Radeon Software Performance Tuning Preset

 

emmzo

Posts: 280   +247
Again learn before you speak!

It turns out that AMD Rage Mode is not a genuine overclocking feature. Instead, the company likened it to a user profile. AMD officially categorizes it as a Radeon Software Performance Tuning Preset

Lol, not a genuine overclocking feature refers to the fact that it is not tweakable. A Radeon Software Performance Tuning Preset means that Rage Mode is a fcking preset and when it is selected it will allow the system to find the highest stable clock speeds available. So it`s an OC profile where you can`t change the parameters. I don`t think that I can dumb it down more, but it seems you are really slow. Learn to read before you speak! Also, read more than one site and see they all refer to Rage mode=overclocking profile. Also read how AMD will reimburse your card if this OC mode fries it.
 
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grumblguts

Posts: 393   +347
Well intels is no use they dont have pci4.0 in any system. and the onyl way I can see them getting it to work on AMD is to ask for AMD to help them.
why would they consider doing that ?
 

HardReset

Posts: 1,070   +660
OK, so now it seems AMD's SAM is nothing else than renamed BAR resize. Partly.

Like Microsoft says: https://docs.microsoft.com/en-us/windows-hardware/drivers/display/resizable-bar-support

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. In particular, we don't want to see the display go blank and back up during this process. It is important to have smooth transition between the firmware displayed image, the boot loader image and the first kernel mode driver generated image. It is guaranteed that no PCI transaction will occur toward the GPU while the renegotiation is taking place.

That essentially means Windows needs GPU with BIOS that supports resizable BAR. I have very few Linux knowledge but if I understand correctly, Linux does NOT need GPU BIOS support to use this feature.

It just seems AMD SAM is nothing else than guaranteed-to-work resizable BAR conditions for Windows. AMD 6000-series GPU's have BIOS support and 500-series motherboards must have new enough AGESA to have resizable BAR support if they are paired with Ryzen 5000-series (those CPU's does not work with too old AGESA).

Seems pretty simple now unless I missed something.