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
 

Shivansps

Diamond Member
Sep 11, 2013
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With SAM, we get 64GB/s fed to the CPU, instead of 25-ish for the DDR4-RAM. Thats quite a difference. Look ahead and PCIex gen 5 will deliver 128GB/s to the CPU. Might as well throw those sticks of RAM out the window, just buy a AMD 8900XT with 48 Gigs of GDDR7 feeding the CPU with the SAM-Ex-ALLCPU feature.. ;D

Well i was thinking exactly about this... what AMD managed to do is probably to add the GPU memory address range after the main system ram range... This should make possible, at least in theory, to use GPU memory as system ram.
 
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DDH

Member
May 30, 2015
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300W Total Board Power for RX 6900XT and 6800 XT and 250W TBP for 6800 is with USB-C 30W.

Have a nice day :).
I wondered about that. Total board power would theoretically mean the max power the board would chug under the most strenuous load, so while 100% GPU load and USBc output?

Have you seen confirmation of this somewhere?

Nvidias 20 series had USBC right? So were their tbp numbers inclusive of USBC power delivery too?
 

Elfear

Diamond Member
May 30, 2004
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Well the 3080 does better vs old architecture at 4k vs 1440p, most just assumed this was because of being more CPU bound, which may be part. But seemed more due to it's design, sort of reminded me of was it Vega, which also was relatively slower at lower resolutions but did better as resolution increased.

Hardware Unboxed did an interesting analysis about the doubling of the FP32 throughput in Ampere being the reason they really come alive at 4k. Link to post with more info.
 

Glo.

Diamond Member
Apr 25, 2015
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I'm giving serious consideration to an all-AMD build, which I've never done before. 5900X + 6800XT, anyone? Hmmm. Maybe.

I'll see if independent reviews push me over the edge.
I myself will build, for my first time in my life full AMD build with first time AMD GPU owner here :)

Ryzen 5 5600 + Navi 23 based GPU will fit the bill :).
 

Glo.

Diamond Member
Apr 25, 2015
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I wondered about that. Total board power would theoretically mean the max power the board would chug under the most strenuous load, so while 100% GPU load and USBc output?

Have you seen confirmation of this somewhere?

Nvidias 20 series had USBC right? So were their tbp numbers inclusive of USBC power delivery too?
Yes. No. Maybe?

Just wait for reviews, till this will be proven right or wrong ;).
 

sze5003

Lifer
Aug 18, 2012
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I'm giving serious consideration to an all-AMD build, which I've never done before. 5900X + 6800XT, anyone? Hmmm. Maybe.

I'll see if independent reviews push me over the edge.
Also thinking of this for the first time too. But I have a gsync only monitor so not really convinced 100% yet.
 

PhoBoChai

Member
Oct 10, 2017
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Hardware Unboxed did an interesting analysis about the doubling of the FP32 throughput in Ampere being the reason they really come alive at 4k. Link to post with more info.

That's the correct analysis. Some graphics workload are resolution independent, as in they don't change much, relative to the pixel increase of higher resolution.

What scales with res, are compute and pixel shaders, screen space effects, RT, etc.

3080 and 3090 has far too much FP32 ALUs for its identical to 2080Ti performance in vertice, geometry, and raster. And only a tiny bit more texture performance. So its imbalanced. Requires high res to showcase the 2x FP32 gains.

Big Navi doesn't have an excess of compute like GCN, relative to front & back end performance. It's more balanced for graphics/gaming, and performs well across the different resolutions.
 
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Justinus

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Oct 10, 2005
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You know, "Above 4G Decoding" sure sounds an awful lot like resizable/large BAR support.... A.K.A. Smart Access Memory...

I wonder if it will work on systems where the driver detects full mapping of VRAM, if it will be limited due to some proprietary synergy with Zen 3, or if it will be artificially locked out.
 

randomhero

Member
Apr 28, 2020
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Has anyone thought of IC in CDNA?
Rumoured die size is huge, close to reticle limit. There is no graphics and video output related hardware, although it has fp64 and AI related hardware and extra 48 CU.Memory controller should be about same since it uses 4096 bit HBM.
 
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PhoBoChai

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Oct 10, 2017
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Has anyone thought of IC in CDNA?
Rumoured die size is huge, close to reticle limit. There is no graphics and video output related hardware, although it has fp64 and AI related hardware and extra 48 CU.Memory controller should be about same since it uses 4096 bit HBM.

It's going to have either tweaked CUs to accelerate tensor ops, or dedicated tensor cores. Lots and lots of SRAM cache for HPC and big data acceleration.
 

uzzi38

Platinum Member
Oct 16, 2019
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Some supposedly ray tracing Shadow of the Tomb Raider 1440p and 4K benches of the 6800


Setting Ray Tracing High 1440p 80 Fps 4K 46 Fps
One more for you too.

So the 6800 looks like it's between the 3070 and 3080 here. Like right in the middle.
61a055ebefc0ecf854be7bce4cad53f5.jpg
 

PhoBoChai

Member
Oct 10, 2017
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Some supposedly ray tracing Shadow of the Tomb Raider 1440p and 4K benches of the 6800


Setting Ray Tracing High 1440p 80 Fps 4K 46 Fps

It's highest setting for RT Shadows in the menu.

46FPS @ 4K

80FPS @ 1440p

Max settings.

6800.

WTF! That's faster RT than expected from all the rumors.

6800 has 60 SM, so 60 "Ray Accelerators", vs 68 in the 3080.
 
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uzzi38

Platinum Member
Oct 16, 2019
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It's highest setting for RT Shadows in the menu.

46FPS @ 4K

80FPS @ 1440p

Max settings.

6800.

WTF! That's faster RT than expected from all the rumors.

6800 has 60 SM, so 60 "Ray Accelerators", vs 68 in the 3080.
I bet you now that the whole Infinity Cache thing is helping out a huge deal.

At the same time though, I'm not expecting a huge improvement to RTRT as you move up the stack. This looks only 10% behind the 3080, if I were to guess the 6800XT and 6900XT will probably be closer to the 3080 with the 3090 on top.

(Not to take anything away from AMD - this sort of performance is well past what I expected from the hugely cut down 6800).
 

kurosaki

Senior member
Feb 7, 2019
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I bet you now that the whole Infinity Cache thing is helping out a huge deal.

At the same time though, I'm not expecting a huge improvement to RTRT as you move up the stack. This looks only 10% behind the 3080, if I were to guess the 6800XT and 6900XT will probably be closer to the 3080 with the 3090 on top.

(Not to take anything away from AMD - this sort of performance is well past what I expected from the hugely cut down 6800).
I'm seeing it in front of me, how Lisa just wawes off the comments around the top notch RT performance after the flaming hot reviews with an, "of course our RT is better".
 
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soresu

Platinum Member
Dec 19, 2014
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I'm seeing it in front of me, how Lisa just wawes off the comments around the top notch RT performance after the flaming hot reviews with an, "of course our RT is better".
Even if RT isn't perfect this gen it's still enough to get the job done for a first shot, and you just know that RDNA3 will bring improvements as Zen3 did for gamers.

Cue nVidia trying to push out Far Cry fully Path Traced edition to make AMD look bad in the interim.
 
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