Discussion RDNA4 + CDNA3 Architectures Thread

[DisEnchantment]

With the GFX940 patches in full swing since first week of March, it is looking like MI300 is not far in the distant future!
Usually AMD takes around 3Qs to get the support in LLVM and amdgpu. Lately, since RDNA2 the window they push to add support for new devices is much reduced to prevent leaks.
But looking at the flurry of code in LLVM, it is a lot of commits. Maybe because US Govt is starting to prepare the SW environment for El Capitan (Maybe to avoid slow bring up situation like Frontier for example)

See here for the GFX940 specific commits

History for llvm/lib/Target/AMDGPU - llvm/llvm-project

The LLVM Project is a collection of modular and reusable compiler and toolchain technologies. - History for llvm/lib/Target/AMDGPU - llvm/llvm-project

github.com

Or Phoronix

More AMD "GFX940" Enablement Work Landing In LLVM - Phoronix

www.phoronix.com

There is a lot more if you know whom to follow in LLVM review chains (before getting merged to github), but I am not going to link AMD employees.

I am starting to think MI300 will launch around the same time like Hopper probably only a couple of months later!
Although I believe Hopper had problems not having a host CPU capable of doing PCIe 5 in the very near future therefore it might have gotten pushed back a bit until SPR and Genoa arrives later in 2022.
If PVC slips again I believe MI300 could launch before it

This is nuts, MI100/200/300 cadence is impressive.



Previous thread on CDNA2 and RDNA3 here

Question - Speculation: RDNA3 + CDNA2 Architectures Thread

Man I have been dying to make this one for a while now. First rumours for RDNA3 are here so new thread time! Just going to start off with this one for now: kopite7kimi on Twitter: "@VideoCardz Ah, I mean a simple mcm design with 10240 cores is not enough. Because the lift from RDNA2 to RDNA3...

forums.anandtech.com

 

[marees]

New wgp + high clock, should be between XT and XTX
Mlid also always stays between XT and XTX, in worst scenario like XT

Let us see

4/60% more shaders = 1.06x
22% more clocks = 1.06x × 1.22x == 1.29x
5% to 10% more ipc = 1.29x * 1.1x (max) = 1.4x

So yeah, 2% to 5% more than 7900xt possible assuming clock & ipc targets are met (within the power budget & memory speed constraints)

Realistically, I expect it to just fall short of the 7900xt (due to power & memory speed constraints)

 

[SolidQ]

5700XT vs 6700XT. Despite 6700XT have less bandwidth and bus, but same CU(Zero ipc between RDNA1 and RDNA2)

 

[marees]

5700XT vs 6700XT. Despite 6700XT have less bandwidth and bus, but same CU(Zero ipc between RDNA1 and RDNA2)

The hype was real for RDNA 2 (navi 22). It was branded as nv killer targetting performance between 2080 super & 2080 ti. It delivered

This time there is no incentive for AMD to beat 7900xt with navi 48 as both cards can continue to be produced in parallel

Edit:
Also infinity cache

 

[ToTTenTranz]

That seems optimistic. I expect raster to be between 7900gre & 7900xt based on available information

The top Navi 48 with 64CUs at 3.1GHz should do 50.8 TFLOPs, whereas the 7900XT with 84CUs at 2.4GHz does 51.7 TFLOPs.
If there are no IPC improvements then these should be about equal, but otherwise the top Navi 48 should be a bit better.



I do wonder if Navi 48's 16GB VRAM will eventually become a bottleneck during its lifetime, though.

 

[marees]

I do wonder if Navi 48's 16GB VRAM will eventually become a bottleneck during its lifetime, though.

The memory speed could be a bottleneck right at the beginning

VRAM size is useful to segment the market. Like between 5700xt & Radeon VII

 

[marees]

Yet another "our rumours vs MLID rumours".
When will RDNA 4 come out in the end? Answer in a month. If he turns out correct, I'll be vindicated that it made no sense for pretty much all RDNA 4 drivers to be already in Linux and yet the non-selling RDNA 3 to linger until 2025.

Also his perf predictions are embellished since he's an AMD proponent, but it's very much in the ballpark of our predictions and my earlier napkin math: Roughly between 7900 XT and XTX Raster (he says 4080, which I don't buy), about 4070 Ti Raytracing (and again he says 4070 Ti Super which I also don't buy).

MLID doubling down

Against him:
Powercolor & other board partners
Kyle Bennet (hardocp)
Wccftech
Videocardz
Toms
Techpowerup
etc. etc.

 

[marees]

MLID doubling down

Against him:
Powercolor & other board partners
Kyle Bennet (hardocp)
Wccftech
Videocardz
Toms
Techpowerup
etc. etc.

7700xt power consumption
7900xt raster
4070 ti super RT
4070 super price ????

 

[maddie]

The hype was real for RDNA 2 (navi 22). It was branded as nv killer targetting performance between 2080 super & 2080 ti. It delivered

This time there is no incentive for AMD to beat 7900xt with navi 48 as both cards can continue to be produced in parallel

Edit:
Also infinity cache

Why would AMD want to continue producing the 7900 & 7800 models? They aren't the cheapest designs to make.

 

[marees]

Why would AMD want to continue producing the 7900 & 7800 models? They aren't the cheapest designs to make.

I am guessing as a stop gap until the RDNA 5 equivalent of 6700xt makes an appearance

Btw the packaging costs of n31 should be reasonable compared to CoWoS

 

[maddie]

I am guessing as a stop gap until the RDNA 5 equivalent of 6700xt makes an appearance

Btw the packaging costs of n31 should be reasonable compared to CoWoS

It's not just the packaging, it's also the sheer area of silicon needed. Also, why mention CoWoS in this context?

Supposedly, N48 = 230-240 mm^2 (N4) versus N31 = 300 mm^2 (N5) + 225 mm^2 (N6) + advanced packaging.

N48 is going to be much cheaper to produce.

 

[marees]

N48 is going to be much cheaper to produce.

True. N48 is a replacement for N43

N42 & N41 both are scrapped. Without any replacements.

So AMD has to keep producing N31 to meet the demand of N42. Sunk costs / investments should be able to keep the production line going for N31

 

[Tuna-Fish]

True. N48 is a replacement for N43

N42 & N41 both are scrapped. Without any replacements.

Based on the memory interface, N48 is a replacement for N32. N43 is a replacement for N33. N31 doesn't seem to have a direct replacement.

Unless N48 really misses expectations on RT, I suspect N31 will not stay in production because there will be a lot of benchmarks where N48 beats it, and this makes it harder to sell. Also, it's much, much more expensive to make, so unless AMD can get a much better price for it, they'd rather sell you a N48.

 

[marees]

N43 is a replacement for N33.

N44 is the replacement for N33

N43, N42, N41 are all above N44. All got scrapped
N48 replaced N43

No replacements for scrapped N42 & N41. Which is why N31 should continue

 

[marees]

Shipping manifests also have so far revealed only 4 in total across n44 & n48

https://twitter.com/x/status/1828316425209164079

If AMD launched these 4 SKUs today, then they could price them exactly at

$600 (4070 ti super)
$500
$400
$300 (4060 ti 8gb)

!!!

https://twitter.com/x/status/1828492927523545233

 

[Mahboi]

In a way, I have some good hopes for this gen.
I don't expect much, but AMD always shone precisely at realistic, decent cost midrange. This is perfect. It's the right amount of RAM, it's nothing fancy but nothing needlessly expensive.
Crossing fingers to see them pop by Oct-Nov at most and to see them actually shine in the $500-600 range with great overall perf & power draw.

 

[marees]

This leak might be A0, which is not the final revision.

How many versions does the hardware usually undergo ?

This has been shipping since april

AMD Radeon RX 8000 "RDNA 4" Graphics Card With Flagship Navi 48 XTX GPU Spotted

AMD's next-generation flagship graphics card within the Radeon RX 8000 "RDNA 4" family has been spotted using the Navi 48 XTX GPU.

wccftech.com

 

[adroc_thurston]

N43, N42, N41 are all above N44. All got scrapped

There was a 40.

How many versions does the hardware usually undergo ?

Not many, GPUs are usually shipped early since you can work around lotsa errata in the driver.

 

[igor_kavinski]

Not many, GPUs are usually shipped early since you can work around lotsa errata in the driver.

I swear if RDNA4 is buggy...

Spoiler

I'll buy it when it's on sale

 

[SolidQ]

Which is why N31 should continue

Isn't N48 replace n31?

 

[marees]

Isn't N48 replace n31?

N48 is below 7900xtx in raster
Maybe equal to 7900xt in raster

Clearly there is a place for 7900xtx (price depends on 5070/5080)
Maybe even 7900xt since it has more vram (but with a significant discount to $650/$600)
7900 gre sells for $530 today & can continue for the same price (or $500)

 

[SolidQ]

Clearly there is a place for 7900xtx

I think it's same situation Radeon 5700XT vs Radeon 7(more Vram and 6+% faster), but in some games 5700XT beat R7

Interesting this. PS5pro have 300tops, wonder how much it has RDNA4

 

[adroc_thurston]

Isn't N48 replace n31?

N32.

 

[branch_suggestion]

N21>N31>N/A
N22>N32>N48
N23>N33>N44

The goal for a replacement is to have similar or lower BoM to the previous part with a significant PPA bump.
If ordered by perf, it should go.

N31>N48>N21>N32>N44>N22>N33>N23

Yes, I do think N44 will just beat N22 so long as VRAM isn't an issue.
N32 and N48 end up in the same relative spot, roughly between the cutdown and full die of the previous gen flagship.
I do firmly believe that N32 was built to beat N21 by 5-10%, RDNA3 just had to be flawed.

 

[leoneazzurro]

N21>N31>N/A
N22>N32>N48
N23>N33>N44

The goal for a replacement is to have similar or lower BoM to the previous part with a significant PPA bump.
If ordered by perf, it should go.

N31>N48>N21>N32>N44>N22>N33>N23

Yes, I do think N44 will just beat N22 so long as VRAM isn't an issue.
N32 and N48 end up in the same relative spot, roughly between the cutdown and full die of the previous gen flagship.
I do firmly believe that N32 was built to beat N21 by 5-10%, RDNA3 just had to be flawed.

That's very probable in raster, for RT it will be quite probably N48>N31if the rumors about the vastly improved RT output are correct.

 

[SolidQ]

for RT it will be quite probably N48>N31

I'd assuming N48 will beat N31, in Star Wars/Avatar, because there only RT mode.