AMD's Graphics Core Next Preview: AMD's New GPU, Architected For Compute
by Ryan Smith on December 21, 2011 9:38 PM ESTFinal Words
As GPUs have increased in complexity, the refresh cycle has continued to lengthen. 6 month cycles have largely given way to 1 year cycles, and even then it can be 2+ years between architecture refreshes. This is not only a product of the rate of hardware development, but a product of the need to give developers time to breathe and to absorb information about new architectures.
The primary purpose of the AMD Fusion Developer Summit and the announcement of the AMD Graphics Core Next is to give developers even more time to breathe by extending the refresh window backwards as well as forwards. It can take months to years to deliver a program, so the sooner an architecture is introduced the sooner a few brave developers can begin working on programs utilizing it; the alternative is that it may take years after the launch of a new architecture before programs come along that can fully exploit the new architecture. One only needs to take a look at the gaming market to see how that plays out.
Because of this need to inform developers of the hardware well in advance, while we’ve had a chance to see the fundamentals of GCN products using it are still some time off. At no point has AMD specified when a GPU will appear using GCN will appear, so it’s very much a guessing game. What we know for a fact is that Trinity – the 2012 Bulldozer APU – will not use GCN, it will be based on Cayman’s VLIW4 architecture. Because Trinity will be VLIW4, it’s likely-to-certain that AMD will have midrange and low-end video cards using VLIW4 because of the importance they place on being able to Crossfire with the APU. Does this mean AMD will do another split launch, with high-end parts using one architecture while everything else is a generation behind? It’s possible, but we wouldn’t make at bets at this point in time. Certainly it looks like it will be 2013 before GCN has a chance to become a top-to-bottom architecture, so the question is what the top discrete GPU will be for AMD by the start of 2012.
Moving on, it’s interesting that GCN effectively affirms most of NVIDIA’s architectural changes with Fermi. GCN is all about creating a GPU good for graphics and good for computing purposes; Unified addressing, C++ capabilities, ECC, etc were all features NVIDIA introduced with Fermi more than a year ago to bring about their own compute architecture. I don’t believe there’s ever been a question whether NVIDIA was “right”, but the question has been whether it’s time to devote so much engineering effort and die space on technologies that benefit compute as opposed to putting in more graphics units. With NVIDIA and now AMD doing compute-optimized GPUs, clearly the time is quickly approaching if it’s not already here.
Larrabee As It Was: Scalar + 16-Wide Vector
I can’t help but to also make a comparison to Intel’s aborted Larrabee Prime architecture here. There are some very interesting similarities between Larrabee and GCN, primarily in the dual vector/scalar design and in the use of a 16-wide vector ALU. Processing 16 elements at once is an incredibly common occurrence in GPUs – it even shows up in Fermi which processes half a warp (16 threads) a clock. There are still a million differences between all of these architectures, but there’s definitely a degree of convergence occurring. Previously NVIDIA and AMD converged around VLIW in the days of the graphical GPU, and now we’re converging at a new point for the compute GPU.
Finally, while we’ve talked about the GCN architecture in great detail we haven’t talked about how to program it. Of course there’s OpenCL, but with GCN there’s going to be so much more. Next week we will be taking a look at AMD’s Fusion System Architecture, a high-level abstraction layer that will make GPU programming even more CPU-like, an advancement necessary to bring forth the kind of heterogeneous computing AMD is shooting for. We will also be taking a look at Microsoft’s C++ Accelerated Massive Parallelism (AMP), a C++ extension to bridge the gap between current and future architectures by allowing developers to program for GPUs in C++ even if the GPU doesn’t fully support the C++ feature set.
It’s clear that 2011 is shaping up to be a big year for GPUs, and we’re not even half-way through. So stay tuned, there’s much more to come.
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hammer256 - Friday, June 17, 2011 - link
It's good to see AMD more committed to the GPGPU. I use GPGPU for neural network simulations, and currently the default choice has been Nvidia with CUDA. It would be nice to see some competition in this space.From the article it sounds like AMD knows to put a lot of emphasis on the software side of things for the developers. Hopefully they'll have a capable programming system that's as good as CUDA, maybe even better.
Finally, Given AMD's strategies in the past with medium sized GPU chips and multi-GPU for high-end, hopefully they'll put sufficient emphasis into support for easier multi-GPU programming.
Exciting times indeed.
krumme - Friday, June 17, 2011 - link
What a pleasure to read articles like this. I would gladly pay for it, more directly, so to speak.Some animations or video, especially for us less tech savvy, would be highly appriciated too.
Competition for x86 is comming ! :)
mczak - Friday, June 17, 2011 - link
I wouldn't really call it radical, Cayman already had the same theoretic 1/2 performance for FP64 adds compared to FP32. Muls/FMAs though are now 1/2 too it seems (though it might not extend to all products) whereas it was 1/4 on Cayman. Still, a factor two is not what I'd call a "radical" improvement.ahmedz_1991 - Friday, June 17, 2011 - link
I really appreciated the letters A M D. Since Athlon, one could feel that AMD is lagging behind Intel more and more, but now with them beingh the first successful CPU\GPU combination (Llano out there now ) now AMD can make their own way and API's even into OS's just like what Intel and NVidia always do. This way I'm more than sure that we'll see titles (apps and games ) with the unified AMD brand instead of those ( meant to be played ) or ( smart solution ) with some stupid stars for Core i3,5 or 7frozentundra123456 - Wednesday, December 21, 2011 - link
Well, technically Sandy Bridge is also a CPU/GPU combination, and I think I would call it successful. Granted, the graphics are not up to AMD levels, but their CPU performance is much better. And considering the debacle of Bulldozer and the architecture that was not optimized for current software, AMD will have to do a much better job of integrating their hardware with software than they have done so far.haukionkannel - Friday, June 17, 2011 - link
So maybe not big upgrades in graphic power, but improvement in computing power. Its really good for CPGPU usage. It allso makes it easier to run physic calculations in AMD GPUs.Hmm... It allso means that more silicon space is neede for same graphic power...
Interesting to see how it all sums up.
Targon - Saturday, June 18, 2011 - link
Right now, there has been a shortage of software that really pushes the graphics limits, mostly because you have the substandard Intel graphics out there that still has a significant market share. How many games out there really make you feel that a Radeon 6970 just isn't enough? The polygon count for objects(characters) in games have not been going up as much as more world detail has been going in.Now, when developers want to try aiming for 5 million polygon figures in games, THAT is where there will be a bigger demand for more graphics power, and with that level of detail, the CPU power needed to properly animate the objects needs to be higher. This is where all of this work with GPU compute comes in, to handle all the complexities of properly animating these super-high detailed objects.
I will note that The Witcher 2 is one of the first games I have seen in a long time where CPU power needs to be higher than a Phenom 2 945, and I am waiting for the AMD Bulldozer core CPUs(not APUs) to come out to see how big of an improvement it will make.
IlllI - Friday, June 17, 2011 - link
can someone explain all this to me? lol this is all beyond my understandingtipoo - Saturday, June 18, 2011 - link
They are making GPU compute much more capable and possible, in a nutshell. This will greatly increase the processing speed of many tasks on computers.khimera2000 - Sunday, June 19, 2011 - link
AMD has CPU and GPU, but there seperate. They want this to change.There combining the CPU and GPU so that they are more able to talk to each other, and do the tasks there best at. this is done by remaking the way they build video cards.
C++... great for CPU not so great for gpu... they want to change this.
Out of order operations suck on the GPU. they want to change this, so it can hammer through more work faster.
There also throwing in a bunch of tools to help tell developers where there messing up in this regard.
fusion APUs will have a nice trick... they will be able to talk to each other without needing to send information back to memory. Imagion passing letters but having to use fedex, this would be like a move to passing letters in class (no fedex) its quicker :) and your mail isint delayed.
APU will talk over PCI-E... Im wondering how that will work to 0.o