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Intel presentation reveals the future of the CPU-GPU war
http://www.beyond3d.com/content/articles/31
Intel presentation reveals the future of the CPU-GPU war Published on 11th Apr 2007, written by TeamB3D for Consumer Graphics - Last updated: 11th Apr 2007 Introduction Back in February we reported that Intel's Douglas Carmean, new Chief Architect of their Visual Computing Group (VCG) in charge of GPU development at Intel, had been touring universities giving a presentation called "Future CPU Architectures -- The Shift from Traditional Models". Since then he's added a few more major university stops, and now the feared B3D ninjas have caught up with him. Our shadow warriors have scored a copy of Carmean's presentation, and we've selected the juicy bits for your enjoyment and edification regarding the showdown that Intel sees as already underway between CPU and GPU makers. http://www.beyond3d.com/images/artic...Image1-big.jpg http://www.beyond3d.com/images/artic...ure/Image2.jpg http://www.beyond3d.com/images/artic...ure/Image3.jpg After a fairly standard review of CPU development over the last thirty years, a serpent is detected in the CPU boys' garden of eden, threatening their supremacy. "CPU profit margins are decreasing. GPU margins are increasing." As the old saying goes, "Follow the money!" and you'll rarely be lead astray. But where has this serpent come from? http://www.beyond3d.com/images/artic...ure/Image4.jpg http://www.beyond3d.com/images/artic...ure/Image5.jpg http://www.beyond3d.com/images/artic...ure/Image6.jpg http://www.beyond3d.com/images/artic...ure/Image7.jpg Ah ha, NVIDIA and ATI are revealed as the wannabe usurpers, and the GPU programability trends that began with 2001's NV20 DX8 capabilities have now grown to be enough of a threat to gain even the attention of mighty Intel. Given that Carmean first began giving the original form of this presentation in 2005, one might wonder how large a part the rationale displayed here played in AMD's acquistion of ATI which was first proposed in December of that year. http://www.beyond3d.com/images/artic...ure/Image8.jpg http://www.beyond3d.com/images/artic...ure/Image9.jpg http://www.beyond3d.com/images/artic...re/Image10.jpg http://www.beyond3d.com/images/artic...re/Image12.jpg Now the clues as to where Intel's VCG are going with their graphics architecture appear. You're asked to visualise an in-order 4-thread 'throughput' core at 10mm2 and consuming only 6.25W. In theory, that'd look like a pretty weak CPU, with less than one third the single- threaded performance of current processors. The catch, however, is that they'd strap on a super-wide Vec16 FPU! It would likely be programmer-controlled via new instructions, so you'd use it as you see fit, but for graphics it would make some sense to think of it as working on scalar operations for four quads (2x2 pixels) at a time. Now, pack a given die area with enough of those small cores, Intel says, and et-voila, a multi-threaded, very-wide vector processor that scales according to understood CMP and CMT ideology. But it's also one that might require very significant compiler and software engineering effort to run fast, given what we know of current CPU and GPU architectures. It should once again be noted that each throughput processor would have ~30% the performance of a traditional CPU for single-threaded code, according to the slides, but for only 1/5th of the area even though it hosts a Vec16 unit. So again, the scaling opportunity of an architecture like that seems somewhat promising, even if not all applications it could run fully exploit the new FPU. Legacy code obviously wouldn't benefit at all from it. So the question is, does the core support x86 instructions at all? If single-threaded performance is still roughly acceptable, it might make some sense for it to do so, and then you could think of the Vec16 FPU as an 'on-core' coprocessor that exploits VLIW extensions to the x86 instruction set. Or, the entire architecture might be VLIW with absolutely no trace of x86 in it. Obviously, this presentation doesn't give us a clear answer on the subject. And rumours out there might just be speculating on Larrabee being x86, so that doesn't tell us much either. http://www.beyond3d.com/images/artic...re/Image13.jpg http://www.beyond3d.com/images/artic...re/Image14.jpg http://www.beyond3d.com/images/artic...re/Image15.jpg Add in thread synchronisation, cross thread communications and a completely shared cache setup and threads have an efficient means to communicate while processing. It does look quite different from what Intel is researching with Polaris aka the Terascale Initiative, but that doesn't mean it couldn't be quite efficient indeed. That remains to be seen, of course. The slides do mention fixed-function units, but that doesn't really mean much, and it's hard to say how much of a focus Intel will have on implementing those blocks efficiently - especially so since these would be unused during non-graphics processing, and the previous slides clearly pointed out the advance of GPGPU as one of the key reasons behind the development of this new architecture for Intel. It is not unthinkable that Intel would try to maximize the amount of work done in these processors, rather than in fixed-function units. For example, many of the operations achieved in the ROPs, such as blending, could be done there. Triangle setup wouldn't be too hard either. But what about rasterization, antialiasing, texture addressing and anisotropic filtering, etc.? There's more to a good graphics processor than big SIMD units and high aggregate bandwidth but it's a big step in the right direction, obviously. And it's not like the described architecture would really be a traditional GPU anyway, with only 4 threads per core (arguably, that should be compared to G80's 12 warps/multiprocessor) and a huge cache! Either way, it will be quite interesting to see what Intel comes up with for the "fixed-function units" part of the chip. If it's good enough, this might be a real competitor in the 3D space. Otherwise, it'd likely only compete for GPGPU mindshare. http://www.beyond3d.com/images/artic...re/Image16.jpg http://www.beyond3d.com/images/artic...re/Image17.jpg http://www.beyond3d.com/images/artic...re/Image18.jpg http://www.beyond3d.com/images/artic...re/Image19.jpg http://www.beyond3d.com/images/artic...re/Image20.jpg http://www.beyond3d.com/images/artic...re/Image21.jpg http://www.beyond3d.com/images/artic...re/Image22.jpg Now here's where things really get interesting. Intel provides their vision of where the fault lines and relative advantages for CPU vs GPU are by application types. It is particularly interesting to note that they place video processing firmly in the CPU camp, and yet all current premium video solutions for high-end codecs rely on GPU power to accelerate this function smoothly. Of course, part of that is dedicated silicon for the decoding, but many of the video quality enhancements on G80 are done in the shader core, presumably through CUDA! It should be noted there that one of the points Intel brings forward is that GPUs are weak at "communciation between elements". That has been traditionally true, but it is certainly also one of the things that CUDA's Parallel Data Cache, aka Shared Memory, is trying to fix. NVIDIA's goal there definiely was to increase their addressable market. It won't fix the problem completely. GPUs are still awful at *creating* complex data structures, for example, among many other things. But it's a step in the right direction, and it highlights that NVIDIA and AMD are ready to change how their GPUs work to get all those GPGPU dollars, just like Intel is ready to change how its CPUs work to try and make sure that doesn't happen. Finance is another area where Intel might be underestimating GPU vendors, but then again, that probably depends on how you define Finance... There's also a fairly strong implication in these slides that there could be a serious struggle for the hearts and minds of ISVs brewing dead ahead, and their willingness (or not) to be convinced to "drag applications to the left" could be a major factor in how events play out. Certainly the GPU boys and their devrel teams are very familiar with that kind of battleground. Interestingly, one of our ninjas reports having gotten a few of Intel's acolytes on the side and perceived a nearly staggering lack of appreciation from them for just how important and resource-intensive the software development infrastructure and support side can be. One hopes for their sake that the senior people have a finer appreciation for this element. But when one remembers how many games updated for dual core CPUs last year also included a note that Intel's HT technology (introduced in 2002!) received significant benefits too. . . well, let's say that confidence on that point is hard to come by. http://www.beyond3d.com/images/artic...re/Image23.jpg http://www.beyond3d.com/images/artic...re/Image24.jpg Heaven forbid anyone should forget the real point of the exercise. . . But then one must recall that Carmean is giving this presentation to eager young engineers at universities. In other words, he's looking for recruits in this war, and reminding them there will be booty galore for those on the winning side is a smart strategy. http://www.beyond3d.com/images/artic...re/Image25.jpg A fairly typical summing up, but one that leaves no doubt that Intel both perceives a serious threat from the GPU makers, and also recognizes that this is not a battle that they can afford to lose. Interesting stuff from the man who is in charge of building an architecture for Intel to fight and win this war. Care to comment on this article? You can do so he http://forum.beyond3d.com/showthread.php?p=966262 |
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Intel presentation reveals the future of the CPU-GPU war
Interesting that in the middle of this Intel presentation there is an
AMD "CONFIDENTIAL" slide. -- If you're a horse, and someone gets on you, and falls off, and then gets right back on you, I think you should buck him off right away. - Jack Handey |
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