Discussion RDNA4 + CDNA3 Architectures Thread

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DisEnchantment

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Mar 3, 2017
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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
Or Phoronix

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

 
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ToTTenTranz

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If that was true, then a 3-chiplet (or even 4) variant should have been relatively simple, and it would have in part satisfied the high end market. So I am quite skeptic about that.

Probably the Infinity Fabric glue logic that allows for 2-chip interconnection would need to be larger if it were to allow for 3 and 4-chip. And there would be higher and uneven latencies.
 
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AMD can do anything. They have proven it time and again throughout their history. They just need proper leadership and RTG should have that now after a few (or many?) heads rolled for the RDNA3 debacle.
 

soresu

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If AMD uses MCM it’s because it’s the easiest way to design a newer die. Until more people report on this I have my doubts.
If AMD is using chiplets it's because it's the cheapest way to do everything going forward as nodes become more complicated and lower yield for the same die size, to say nothing of the costs of producing the mask.

Also having smaller dies offers more versatility for multiple SKUs.
 

leoneazzurro

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Jul 26, 2016
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More chiplets = more IO connections = more overhead = larger IO die.
If it would have been done like MI300, sure (and also there, there are multiple I/O dies). But it could have been done differently, like N31 (distributed I/O chiplets) or with VRAM interface on die, and 2.5D connections only servicing the inter-die connection. There are several possibilities there.
 
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leoneazzurro

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Probably the Infinity Fabric glue logic that allows for 2-chip interconnection would need to be larger if it were to allow for 3 and 4-chip. And there would be higher and uneven latencies.
Yeah but uneven latencies are always a thing in GPUs, especially when building the bigger ones. The simple fact of splitting the shader core in two dies adds a penalty if one die needs to access the data present on the other die.
 
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Mahboi

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Which is why I say that Nvdia is (or became long ago) a vertically integrated software company (like apple)

Whereas AMD is still a hardware company.

What Nvdia (& Apple) do will work only for them and not for others

Nvidia was amongst the first to go for unified shaders and Taiwanese/TSMC outsourced manufacturing. They've been able to distort the market enough to make it consume their supply.
I don't know their history enough, but clearly they are a-ok with high volume/high losses while the penny pinchers across the street are afraid of losing a single mm².
Nvidia's perfectly fine with wasting inordinate amounts of money to get partnerships and/or software stacks that pay off, or as you said, vertically integrate.
AMD sees itself as a hardware vendor that wants to respond to market demands. But Nvidia CREATES market demand because they do so much more than just wait for others to request work towards something.
So AMD's always saving every penny and being several steps behind while Nvidia is ok with wasting money to be market and technology leader.

Which is perfectly fine IF you want to be the eternal N°1 and N°2, but isn't going to work if you want to actually overtake the other one...
Why would they risk decreasing their wafer yield for parts that most gamers consider the budget option?
Really REALLY shouldn't have provoked me on this.

That isn't how that works at all LOL. I bought a 7900 XT, I guarantee you I didn't consider the 1000€ bill "budget". I guarantee that any price above $300 isn't budget. AMD doesn't have special commercial rules that don't apply to Nvidia.

And what do you mean "decrease their yields" lol?
You're speaking as if AMD had a necessity to maximise yield while Nvidia somehow would have a Glove of Free Yields like Jensen is a JRPG protagonist.
They're both in the same boat, they even buy at the same Fab lel.

Jensen, the Hero of Raytracia

Actually since both of them have the same yield issues, riddle me this:
- Nvidia makes the 4090, a 144 SM (24 deactivated) 600mm²+ die. All monolithic. All wasting ~10% of their area. Those that had 140 SMs functional? They have 120. Those that had 130? 120. 120? 120. Nvidia wastes area like it's free.
- AMD makes the 7900 XTX, a 96 CU, fully activated, ~500mm² die. It's chipletized. The GCD itself is only 300mm², rest is 6 24mm² MCDs. If the die is imperfect, it gets SKU'd down into a 7900 XT, so you minimise your losses to only dies that have less than 84 CUs functional.

So since the yields are much better on 300mm² than 600mm², and the 300mm² can be maxed or cut down, tell me, which one is obsessed with margins?
I'm not talking "compare final selling price of a 4090 to a XTX and calculate the better margin". Frankly even if you had a full BOM cost of an XTX straight from an AMD paper and the same from Nvidia for the 4090, you'd probably find AMD to have quite better margins but not miraculously better.
I'm talking about comparing the value which AMD places on margins, yield, cost saving, versus the value that Nvidia places on it.

AMD is not "lowering costs". They're "maximising margins by lowering costs". Nvidia puts their money towards next versions of DLSS, Raytracing, cool new things? AMD puts its money towards researching how to penny pinch every mm². And if you're doing a very budget oriented strategy, I got nothing against it. But that is NOT what AMD supporters claim they're doing, on the contrary. They claim that AMD is "doing that so they can compete and beat Nvidia"...except they keep outputting borked stuff, or low risk, low expenditure stuff.

RDNA 3's a failure?
"Oh, respins are TOO EXPENSIVE, fixing it was just impossible, and yes we still lied bold faced about the perf and power draw".
RDNA 3 is a failure, and doesn't get fixed?
"Well, RDNA 4 planned for everything to be chiplets chiplets chiplets to save AMD's precious money, and guess what, it's also all borked for some reason. So instead, you'll get the one monolithic chip that we have. It's 240mm²."

Versus Nvidia calmly fabbing 600mm² monolithic dies.
We know that Raja Koduri screwed them over with his ambitions and then did the same thing to Intel's GPU effort too by overhyping and over-promising. Maybe he's a double agent working for Nvidia. Screwed over the only two viable competitors.
There's several dimensions between Ponte Vecchio and ending up with a 240mm² die as "the best this gen". I find it frankly insulting to my intelligence that AMD supporters defend this as even remotely acceptable. The level of effort here is nothing. For the first time that I can think of, a "new generation" is so lazy that it won't even attain the raw raster power of the last generation's top die. WHILE THAT GENERATION WAS BORKED IN THE FIRST PLACE, HOLY HECK.

"But the die is so smol and all because people want budget things and they didn't have a choice and poor wittle Radeon deserves our love and care and patience and" no. Shut.
The die is small because Nvidia's ok with outputting a 600mm² giant fat hog of a die. Even if they lose area. Even if it's silly expensive.
AMD's not. So they pour all this effort in magical omega chipletized 144WGP monsters, the monsters all get borked like Frankenstein's monsters and then a manager goes "well, let's just completely give up and go for selling only our tiny monolithic die".
And no, it's not "so utterly borked that it's unsellable". RDNA 3 was sold by AMD, you can trust that RDNA 4 could've been sold above the ridiculous mini die. And you can trust that they cancelled anything above that die because the margins wouldn't have been satisfactory enough for Lisa's lofty penny pinching. It's always don't lose yields, don't take risks, SAVE THE PENNIIIIIIIIIIIIIIIIES...

It's always borked things, cancelled things, or cheap things. All the while asking for "understanding their circumstances". All the while we hear more promises of "next gen it'll finally be great".

All the while Nvidia will just make another super expensive 600mm² and the Dragon of Yields eats another spear in the belly.
If we want AMD to start taking risks, first we need to start taking risks ourselves by plopping down full price for their GPUs (good or bad). I still have an unopened ASUS 6800 XT LC card (coasting by on Gigabyte RX 6800). I believe DrMrLordX also has an unopened 7900 XTX. We need more of us to support AMD.
Hello, AMD supporter here, bought the 7900 XT, believed in the marketing when they said "50% better performance, 50% better power efficiency", and when the reviews came out and all the shills said "they have a temporary problem, the drivers will fix this", I believed them too. Less so every month, and ultimately I bought it knowing it was not that good. But it was still 1000€ all the same. It's not budget. It's not something I bought thinking "I'm saving money buying AMD". I bought because it was the best thing to buy at the time. Period.

I am very much supporting Radeon. I am however getting extremely annoyed at the absurd position that their vocal supporters have:
- AMD is our friend that needs our support to fight Nvidia, but AMD is a business that needs to maximise margins
- AMD tries to make great stuff for cheap, but AMD is a business that needs to maximise margins, so expect the production to be cheap, not the final price
- AMD is all about open source and the public interest, but AMD is a business that needs to maximise margins by lowering costs, so they invest a ton less in software than Nvidia
- AMD is "helping fight Nvidia", but AMD is only going to bother putting out a 240mm² die this gen, anything else would be too expensive for their penny pinching goals
- AMD is "trying to lower costs for the public to get good GPUs for cheaper", and will price it as high as Nvidia's competition will allow them to because MUH MARGINS

I have had way, WAAAAY enough of that narrative. I'm extremely sick of it.
You can't be a semi-charity and "this is a business not a charity". You can't be "for the public" and "margins are what we're about". You can't be about lower costs and sell at the highest possible. And more than anything, you can't be the company that "deserves our support" while giving up or derailing everything. RDNA 3 borked? RDNA 4 cut down all the way to a 5700 xt/6600 xt size die? I mean what is that? THAT's what we gotta support so they can "fight Nvidia"?

I am so absolutely sick of these excuses. Either they want to penny pinch so much because it's about lowering the general costs and getting a "good enough" product out for good enough margins(not viable in this industry), either they get their fat margins in and try to get a real, costly, risky high end product out. But you can't have the cake and eat it too. Right now what AMD's been doing since the RDNA 3 failure is not fix anything, not respin, not have a high end product.
And do not dare throw a "well, they couldn't", YES THEY CAN. They supposedly fixed the RDNA 3 power draw problem, so put out a danged 7950 XTX with 20% more clocks. Plan for a die, even if it's monolithic and more expensive, that's not a 240 ridiculous mm² low-end thing. Do not output a failed gen only to follow with a gimped gen! I'd not have said a thing if the top die was just 300-350 mm², but 240 is straight up not even trying.

Remember Thermi? Jensen threw an entire generation with an arch he knew was terrible and yields that were atrocious. Did that stop him? No! Because he takes risks and PUTS HIS MONEY WHERE HIS MOUTH IS!
AMD with TSMC's backing can't even get at least a die half the size of what Nvidia will output?!!! And everything above 240mm² was supposedly "so borked that it wasn't even worth putting on the market"???? F off with that story for babies, they couldn't get their ultra-optimised margins so they just gave up. Just put out a tiny die, say that it's about "helping the budget buyers", price it as high as it'll go, and your supporters will Defend your Honour from any criticisms.

AMD has to take its money and margins, and do something with them, or stop being so margin obsessed.
But the AMD supporters have to stop doing THIS:
Beggar in the lab, gouger in the shop. Failure after failure, disappointment after disappointment, 10 years of the same supporter narrative.
 

Mahboi

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Apr 4, 2024
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Are you saying that you bought it based on the advertised performance even after all the reviews are out? )
Nah, it was a slow fall from hype to disappointment over 4-5 months.
I bought it because I had replaced all my monos with 4K ones, and needed a 4K card.
4090 was way more than I needed, 4080 absolutely did not justify its 1370€ price, XTX had somehow stagnated or slightly risen to 1270€, and I could get a 7900 XT for 975€. And the 4070 Ti was an insult with 12Go VRAM.

I just didn't like getting hyped then left to drop like an old sock. Nobody likes that.
 
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Mahboi

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I guess the history of the question "why N31 flopped so hard" would be as interesting as the question "why death of 20nm unsettled Radeon much harder than nV"
It is honestly surprising that despite being on its way out, I have never heard an explanation on what went goof with RDNA 3.
Heard tons of takes, most of it centering around "the CU has a real electrical design problem", but what the problem actually is, no clue still.
Well, now you know the price of the former.
?
 

soresu

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Dec 19, 2014
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Failure after failure, disappointment after disappointment
RDNA2 was plenty good in the raster gfx arena, they were just behind in the RTRT department.

I'm more annoyed that they are slow walking the software side of things with HIP-RT than anything they are doing on the hardware side.
 
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I bought it because I had replaced all my monos with 4K ones, and needed a 4K card.
Howz it serving you so far? Any deal breaking issues?

What was your previous card?

At some point (I think after Koduri's delays but it could've been well before that), AMD management just stopped paying much attention to gaming because the team wasn't doing anything so extraordinary that could embarrass Nvidia like the R300 did. You see the CPU team executing almost flawlessly with major breakthroughs and setting the industry on fire with each product launch and making the competitor go "BUT BUT BUT" but the GPU team gets all nervous when the management asks them, "Do you have a Geforce killer?" and after seeing what happened to Koduri, they just honestly tell it like it is and management is like, "Oh well. At least it's not a complete disaster" but they tone down the whole effort with budget cuts because they just don't see much promise in spending more on gaming optimized GPUs.

If there is one thing that Jensen does well, he knows the value of competent employees and how to tell good ones from awful ones because he IS a GPU guy/engineer/scientist at heart. He is the original founder, after all. My only beef with him is his fetish in keeping VRAM close to his chest. Otherwise, I would definitely admire him for what he has accomplished.

GPUs are Nvidia's bread and butter and losing is potentially more fatal to them so they do their very best to avoid getting into a losing position. On the other hand, GPUs are not that important for AMD. For AMD to excel at GPUs as much as Nvidia, they would need to spin off their GPU division into a separate, independent entity. Ditto for Intel. When you know that mistakes could sink the entire operation, you are that much more vigilant. The GPU teams at both AMD and Intel know that whatever they do, they can never eclipse the CPU teams' superiority and importance to their respective companies' stakeholders.

So of course, AMD and even Intel may penny pinch when it comes to GPUs but both are trying hard. How can we forget the slow as molasses M$ dotnet mess of a control panel that Adrenaline used to be or Intel's horrible HD Graphics? Both are thousands of miles ahead of where they once were. They would be even further ahead if Nvidia hadn't poached the best and brightest. Intel even spent more than $5 billion on their GPU before it could make a single dollar with a viable product and they still missed the mark.

I'm happy with where AMD and Intel currently are and I would still say that we should support them so they can get better. For me that's very easy coz no matter what anyone else says, current Geforce cards do not make financial sense to me and don't seem magical to me. It's just hyped up hardware that is left to rot as soon as Nvidia launches a new generation whereas AMD keeps refining their drivers for years and benefit their older products with those refinements as long as some required hardware feature isn't missing.

All I can say is, be patient. AMD and/or Intel will strike with decent product(s) causing Jensen to come back down to Earth or maybe even refuse to compete. It's a normal part of competition. Whatever AMD is doing to save costs may actually help them in future if they decide to launch a price war against Nvidia despite having superior product. Nvidia will hemorrhage massively if that comes to pass. Jensen has rested on his laurels before and failed to anticipate the competition. It's just a matter of history repeating itself. I have no problem with AMD saving a bit of money for a rainy day.
 
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soresu

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The most likeliest explanation is that it is lost in translation

Polaris 11 = 2x polaris 14
Navi 23 = 2x navi 24

Likewise
Navi 48 = 2x navi 44
Looking at the Google Translate of the post comes up with this:

AMD only produces Navi48, which packages relatively high-end models through the INFO process. 44 is a small chip cut in half by 48, and uses traditional packaging.
The significance of this is to make MCM graphics GPU before Blackwell.
Original Chinese:

AMD只生产Navi48,通过INFO工艺封装相对较高端型号,44为48切成两半的的小芯片,则使用传统封装。
这样做的意义是赶在Blackwell之前做出MCM的图形GPU

So ye I agree with your assessment.
 

dr1337

Senior member
May 25, 2020
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If the translation says they want to make the first MCM GPU, then that definitely means advanced packaging multiple chips together.


Issue with MCM is that a lot of the IO die can't practically be split in half (?)

Doesn't AMD have a ton of patents about GPU crossbars and such? Also they seem to have a good and established memory and cache chiplet from RDNA3 that they're surely going to reuse. I bet they can pull it off.
 

Joe NYC

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Jun 26, 2021
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If it would have been done like MI300, sure (and also there, there are multiple I/O dies). But it could have been done differently, like N31 (distributed I/O chiplets) or with VRAM interface on die, and 2.5D connections only servicing the inter-die connection. There are several possibilities there.

The Navi 4c showed a way to have perfect modularity and high bandwidth, and power efficient connections between IO dies with silicon bridges, with hybrid bond. That's kind of a nirvana, and it could also work for future Mi400 etc.

The other way is to break part of the modularity, and have 3 different sizes of IO dies, with 2, 4 and 6 channels, but it would require 3 different types of dies. Then, 1, 2 or 3 compute dies would be stacked on top of the IO die.

I doubt 2.5D connection between IO dies will be limited by bandwidth and power inefficiency...
 
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