Question Speculation: RDNA2 + CDNA Architectures thread

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uzzi38

Platinum Member
Oct 16, 2019
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All die sizes are within 5mm^2. The poster here has been right on some things in the past afaik, and to his credit was the first to saying 505mm^2 for Navi21, which other people have backed up. Even still though, take the following with a pich of salt.

Navi21 - 505mm^2

Navi22 - 340mm^2

Navi23 - 240mm^2

Source is the following post: https://www.ptt.cc/bbs/PC_Shopping/M.1588075782.A.C1E.html
 

Hail The Brain Slug

Diamond Member
Oct 10, 2005
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yes, very important to note, because it is a bit of silicon lottery + "benevolence of the devs" to hope that the feature (SAM) is active.

I also want to see if SAM will work with AM4 4xx boards + Zen3 after 2021 firmware update. ...and if all 4xx boards are created equal for Zen3 compatibility.

lots of ***'s to sift through in those posted performance numbers.

Gamers Nexus reporting Rage Mode is not an overclock. It's just a mild power limit increase, which in turn allows for a slightly increased boost clock in games.

No lottery for this. I assume it's because they didn't want to release a card with >300W power limit.

Gamers Nexus also stating AMD has said Rage Mode only accounts for a 1-2% performance increase. AMD also claims smart memory access works automatically and the performance gains they have shown are simply from it being enabled, not because the games have support for it baked in.
 

GodisanAtheist

Diamond Member
Nov 16, 2006
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Wow wow wow what a great showing by AMD! Glad we were able to keep the hype under control folks :p :D

In terms of preliminary benchmarks (naturally, wait for reviews) they exceeded my expectations by a longshot. They even pulled some of the presentation tricks that we were discussion here as well (and one more thing...)

A couple points:

- Prices. Competitive for what they're offering vs the competition, but still too rich for my blood. They know they're going to sell everything they make.

- The fact that they're going to offer a 60 CU N21 at all also strongly suggests they are severely supply constrained at the moment and are harvesting even garbage dies to sell. Its weird because what happens when supply opens up? AMD isn't going to be lopping off 20CUs off a die to sell forever, are they?

-No RT benchmarks. Sounds like they don't have a good partner to show off their RT tech on PC at the moment (everything out there is RTX right now) so they just glossed over it. We know its there and it works (rather well) thanks to some XSX and PS5 game reveals.

More thoughts soon...
 

CastleBravo

Member
Dec 6, 2019
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It will be very interesting to see benchmarks of the 6800XT with a 3800X vs a 5800X to see what the actual performance increase of SAM is.

Will also be interesting to see 6800 XT vs 3080 on an non-Zen3 CPU. The value of the 6800 XT might not look as good if you have to spend another $300+ on a CPU and maybe even a motherboard for it to match/beat the 3080.
 

dacostafilipe

Senior member
Oct 10, 2013
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SAM...sounds to me like this generation's "Cool AMD exclusive feature that will be really awesome if the Devs program for it in each specific game" At least, that is in Ian's article, that it requires Dev work for each game, if it is going to provide any benefit.

Linus talks about a PCIe protocol limitation (Base Address Registers size), so not game specific, but certainly devs could optimise for it.
 
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exquisitechar

Senior member
Apr 18, 2017
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- The fact that they're going to offer a 60 CU N21 at all also strongly suggests they are severely supply constrained at the moment and are harvesting even garbage dies to sell. Its weird because what happens when supply opens up? AMD isn't going to be lopping off 20CUs off a die to sell forever, are they?
I don't think they intend to sell many 6800s, the main one is the XT. 6700XT will probably be much more attractive, IMO, but it isn't ready.
-No RT benchmarks. Sounds like they don't have a good partner to show off their RT tech on PC at the moment (everything out there is RTX right now) so they just glossed over it. We know its there and it works (rather well) thanks to some XSX and PS5 game reveals.
Yeah, I think AMD will shine in DXR 1.1 titles. Performance will be inferior to Ampere's in DXR 1.0 titles.
 

HurleyBird

Platinum Member
Apr 22, 2003
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Could this 'infinity cache' be applied to future RDNA2 iGPUs? something like intel iris graphics l4 cache? bw solution for iGPU perhaps??

I'm doubtful for anything other than a very small cache given that the APUs are optimized for small die sizes, unless perhaps the L3 can be shared with CPU cores. I imagine that's the eventual plan, although I don't know if that's in the cards for the first RDNA2 APU configurations.
 

moinmoin

Diamond Member
Jun 1, 2017
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Could this 'infinity cache' be applied to future RDNA2 iGPUs? something like intel iris graphics l4 cache? bw solution for iGPU perhaps??
AMD likened Infinity Cache to L3 cache in CPUs. I'd expect a RDNA2 based APU to share its L3 cache between CPU and GPU.

It will be very interesting to see benchmarks of the 6800XT with a 3800X vs a 5800X to see what the actual performance increase of SAM is.
AMD has been pretty opaque on that point, but I expect the requirement for Ryzen 5000 and 500 series boards to boil down to PCIe 4 being a requirement for SAM. The comparison with Ryzen 3000 will be interesting indeed.
 

Geranium

Member
Apr 22, 2020
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Looks like 128MB Infinity Cache is true afterall and looks like you dont need to specially program for it.
Also this 'big Navi' has 128 ROP not 64 as rumor suggested.
Hopefully those cards will not have the fate of R9 290X.

Another note: Why no 720p benchmark AMD?? That is the most popular resolution that most people use.
 

soresu

Diamond Member
Dec 19, 2014
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Hmm, there's some more info about the Infinity Cache on AMD's RDNA 2 webpage in the footnotes:


This is in reference to AMD's claim of the following:
- 256-bit 16 Gpbs GDDR6 = 512 GB/s
- 384-bit 19.5 Gpbs GDDR6x = 936 GB/s
- 256-bit 16 Gpbs GDDR6 + 128MB Infinity Cache = 1664 GB/s Effective

A shot directly across the bow of Ampere.
Considering how reliant RT is on memory I wonder how well this would play out at equal TFLOPS?
 

Martimus

Diamond Member
Apr 24, 2007
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Will also be interesting to see 6800 XT vs 3080 on an non-Zen3 CPU. The value of the 6800 XT might not look as good if you have to spend another $300+ on a CPU and maybe even a motherboard for it to match/beat the 3080.
SAM wasn't enabled on their testing with the 3080 and 6800XT. They only enabled it on the 3090 to 6900XT chart.
 

sze5003

Lifer
Aug 18, 2012
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For the 6900xt I assume it's full potential will be better if you have an amd card and board right?

Although for pure gaming use I'm not sure if that would matter much.
 

soresu

Diamond Member
Dec 19, 2014
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So do we know what this 128MB infinity cache is? If I am not mistaken, they said something in the lines of 256bit+infinity cache=Twice the performance of standard 384bit bus. How is this possible? wtf?
The presenter/engineer mentioned that it was modelled on Zen3's L3 cache.
Yeah, I think AMD will shine in DXR 1.1 titles. Performance will be inferior to Ampere's in DXR 1.0 titles.
Makes me wonder if CP 2077 delay has DXR 1.1 zero day goodies in store.
 

Greyguy1948

Member
Nov 29, 2008
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So do we know what this 128MB infinity cache is? If I am not mistaken, they said something in the lines of 256bit+infinity cache=Twice the performance of standard 384bit bus. How is this possible? wtf?

Also do the consoles have it? Will it be present on lower tier cards?

It looks like eDRAM cache. Intel and IBM used/are using it. Transistor count is "only" 28 billion so any transistor cache is smaller.
EDRAM on Wiki
 
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moinmoin

Diamond Member
Jun 1, 2017
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Looks like there's another video from AMD. My apologies if this has been posted already.


Some explanation on AMD Smart Access Memory, Anti-Lag, Radeon Boost, etc.
First time I saw it posted, good video.

Infinity Control Fabric sounds like the Scalable Control Fabric is being expanded outside the device (I imagine that's also part of Infinity Architecture), allowing different devices to know of each other's state and sensors. This may explain why SAM requires Ryzen 5000. This also raises the possibility that RDNA2 reuses the Infinity Fabric hierarchy already known from the Zen CPUs (with Scalable Control Fabric monitoring and controlling everything while Scalable Data Fabric connects all the parts for I/O), with Infinity Cache working the same way as L3 cache in Zen CPU, that is as essentially a crossbar between all cores (= CUs in RDNA2's case).
 

MrTeal

Diamond Member
Dec 7, 2003
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Looks like 128MB Infinity Cache is true afterall and looks like you dont need to specially program for it.
Also this 'big Navi' has 128 ROP not 64 as rumor suggested.
Hopefully those cards will not have the fate of R9 290X.

Another note: Why no 720p benchmark AMD?? That is the most popular resolution that most people use.
Maybe in 2003. The only people playing at 720 are people trying to play shooters at 350FPS and people stuck with 768p laptop screens.
 

Hitman928

Diamond Member
Apr 15, 2012
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Oh... using Rage mode voids the warranty o_O

View attachment 32529

I wouldn't worry about it. As long as you're giving the card decent ambient air, there shouldn't be any issues. Pretty sure this statement is there to cover people using Wattman to crank voltages to crazy levels. Also not sure rage mode even counts as overclocking but maybe AMD can clarify.