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Larrabee ISA Revealed
David Greene writes "Intel has released information on Larrabee's ISA. Far more than an instruction set for graphics, Larrabee's ISA provides x86 users with a vector architecture reminiscent of the top supercomputers of the late 1990s and early 2000s. '... Intel has also been applying additional transistors in a different way — by adding more cores. This approach has the great advantage that, given software that can parallelize across many such cores, performance can scale nearly linearly as more and more cores get packed onto chips in the future. Larrabee takes this approach to its logical conclusion, with lots of power-efficient in-order cores clocked at the power/performance sweet spot. Furthermore, these cores are optimized for running not single-threaded scalar code, but rather multiple threads of streaming vector code, with both the threads and the vector units further extending the benefits of parallelization.' Things are going to get interesting."
If developers are too stupid to code for it, it won't go anywhere. This is sounding a lot like the PS3 architecture in complexity. Parallelism is not that hard to deal with, but you have to know what you're doing. Sadly, few do. Try again in ten years.
Bet they've got some serious CONTROL structures to keep things from getting too KAOTIC....
"Would you believe a GOTO statement and a couple of flags?"
The story title conjured up images of the boxes of ISA cards I've still got sitting around. Ah, the joys of setting IRQs... good times.
512 MB RAM, 20 GB disk, 200 GB transfer, five datacenters. $19.95/month.
Bet they've got some serious CONTROL structures to keep things from getting too KAOTIC.... "Would you believe a GOTO statement and a couple of flags?"
How about a while loop and a continue statement?
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That's what libraries, toolsets and custom compilers are for. If the problem was just silicon we'd have Larrabee by now. What's holding up the train is the software toolchain and software licensing issues.
Don't worry, though. On launch day the tools will be mature enough to use, and game vendors will have new ray tracing games that look fabulous on nothing but this.
I'm hoping the tools will be open but that's a long bet. If they are, Microsoft is done as the game platform for the serious gamer and Intel will make billions as they take the entire graphics market. Intel will make hundreds of millions regardless and a bird in the hand is worth two in the bush, so they might partner in a way that limits their upside to limit their downside risk. That would be the safe play. We'll see if they still have the appetite for risk that used to be their signature. I'm hoping they still dare enough to reach for the brass ring.
Help stamp out iliturcy.
Seriously, most of the Mesa shader assemblers deal with very limited, simple, straightforward shader ISAs. This is icky. We're gonna need a full-on compiler for this.
~ C.
This 300 watts monter, 8086/386/586/x86-64/mmx+sse+ss2+ss3+whateversse compatible mess represents (or should represent) the end of an era. Few people is asking for that kind of product; price and size is more important. It's just Intel trying to hold the market captive forever.
As a structural engineering in training who is starting to cut his teeth in writing structural analysis software, these are truly interesting times in the personal computer world. Technologies like CUDA, OpenCL and maybe also Larrabee are making it possible to simply place in any engineer's desk a system capable of analysing complex structures practically instantaneously. Moreover, it will also push the boundaries of that sort of software beyond, making it possible to, for example, modeling composite materials such as reinforced concrete through the plastic limit, a task that involves simulating random cracks through a structure in order to get the value of the lowest supported load and that, with today's personal computers, takes hours just to run the test on a simple simply supported, single span beam.
So, to put this in perspective, this sort of technology will end up making it possible for construction projects to be both cheaper, safer and take less time to finish, all in exchange of a couple hundred dollars on hardware that a while back was intended for playing games. Good times.
Slashdot, fix your code or at least hire someone who is competent at it to do it for you.
Your post can be summarized as: Intel Giveth; Microsoft taketh away. That's been the formula for far too long.
And that period is almost over.
Help stamp out iliturcy.
There are lots of instructions and other craft inside 80x86 processors that occupy silicon that is never used. A clean break from 80x86 is needed. Legacy 80x86 code can run perfectly in emulation (and need not be slow, using JIT techniques).
What I like most about Larrabee is the scatter-gather operations. One major problem in vectorized architectures is how to load the vectors with data coming from multiple sources. the Larrabee ISA solves this neatly by allowing vectors to be loaded from different sources in hardware and in parallel, thus making loading/storing vectors a very fast operation.
The programming languages that will benefit from Larrabee though will not be C/C++. It will be Fortran and the purely functional programming languages. Unless C/C++ has some extensions to deal with the pointer aliasing issue, that is.
It is over already, Gates retired, remember?
If Intel are smart they will release a chip containing one core (or 2 cores) from some kind of lower-power Core design and a pile of Larabee cores on the one die along with a memory controler and some circuits to produce the actual video output to feed to the LCD controler, DVI/HDMI encoder, TV encoder or whatever. Then do a second chip containing a WiFi chip, audio, SATA and USB (and whatever else one needs in a chipset). Would make the PERFECT 2-chip solution for netbooks if combined with a good OpenGL stack running on the Larabee cores (which Intel are talking about already).
Such a 2-chip solution would also work for things like media set top boxes and PVRs (if combined with a Larabee solution for encoding and decoding MPEG video). PVRs would just need 1 or 2 of whatever is being used in the current crop of digital set top boxes to decode the video.
As for the comment that people will need to understand how to best program Larabee to get the most out of it, most of the time they will just be using a stack provided by Intel (e.g. an OpenGL stack or a MPEG decoding stack). Plus, its highly likely that compilers will start supporting Larabee (Intel's own compiler for one if nothing else).
I don't think so.
I was thinking that. The Larrabees vector unit looks like it could just replace SSE entirely.
Which does raise a question - will Intel keep SSE if it adds in the Larrabee vector unit as yet another legacy feature? I'm guessing it will (sigh).
This isn't really x86, in my opinion; it's x86 with a separate set of very obviously graphics-oriented instructions bolted on top. Since getting decent performance will require using the new instructions and a new programming model almost exclusively, what's the point of the x86 bit? Well, other than marketing reasons and to prevent companies like NVidia releasing their own version, of course...
I don't think we will see this in notebooks for a while. We need to wait and see what the real product looks like (Intel hasn't released any specs), but Google for Larrabee and 300W and you will see the scuttlebut is that this chip will draw very large amounts of power.
Yeah, most x86_64 ABI's use SSE for scalar floating point, so it's too late to remove it. But hey, at least SSE is an improvement over x87.
Was the best movie of all time.
Im skeptical about the future of SIMD and even instruction level parallelism in general for massively parallel processors. The problem with this is that in order to get maximum utiliasation of all of the ALUs in the processor, you have to fill the entire vector with data that you can perform the SAME operation on. This means its up to the programmer or compiler to write highly vectorizable code. If you cant fill these huge 512-bit vectors, arithmetic units are going to be idle. nvidia realised this years ago, and so since the G80 their architectures have been scalar. Without vectors you can run alot more scalar threads while keeping ALL the units busy all the time. Win Win. I'll need some serious convincing if I'm to believe Intel is a real threat to nvidia in this space, especially for GPGPU.
The claim that this is the first time you can get "GPU class rendering in software"... with nothing more than a pixel sampler to help is somewhat dubious. Modern GPUs are, after all a bunch of stream processors with a pixel sampler. So, really, modern GPU graphics is all in software except the sampling.
Oh, hey and anyone here remember the voodoo? That was a big (for the sime) sampler driven by an x86 CPU. Sound familiar?
Sarcasm aside, I want one. The peak performance is high, and the programming model is well known. Also, Linux support is likely to be excellent.
SJW n. One who posts facts.
Articles states that there's hardware support for transcendental functions, but the list of instructions doesn't include any. Anyone know what is/isn't supported in this line?
A larger, more complex superscalar chip core + several smaller, simpler, and bus connected fixed-function units is also the exact design of the Sony CELL processor.
"Would you believe a GOTO statement and a couple of flags?"
How about a while loop and a continue statement?
In C, a continue breaks out of only one nested while or for loop. If you're in a triply nested loop, for example, you can't specify "break break continue" to break out of two nested loops and go to the next iteration of the outer loop. You have to break your loop up into multiple functions and eat a possible performance hit from calling a function in a loop. So if your profiler tells you the occasional goto is faster than a function call in a loop, there's still a place for a well-documented goto.
C++ code can use exceptions to break out of a loop. But statically linking libsupc++'s exception support bloats your binary by roughly 64 KiB (tested on MinGW for x86 ISA and devkitARM for Thumb ISA). This can be a pain if your executable must load entirely into a tiny RAM dedicated to a core, as seen in the proverbial elevator controller, in multiplayer clients on the Game Boy Advance system (which run without a Game Pak present so they must fit into the 256 KiB RAM), or even in the Cell architecture (which gives 128 KiB to each DSP core).
When performing limit analysis, the lowest supported load calculated through the plastic limit (see limit analysis' upper bound theorem) is the lowest possible load that causes the structure to collapse.
I think Anonymous Coward was trying to say that the layman's term for this load amount is the "highest supported load" that doesn't cause collapse.
Oddly enough your post ranks quite highly in that search. Drilling through the forums that show up reveal speculation that a 32-core Larrabee design will use 300W TDP, or roughly 10W per core. There doesn't seem to be any justification for that number although the Larrabee looks like Atom + stonking huge vector array. The Atom only uses 2W, it seems hard to believe that the 16-way vector array would use as much power for each FLOP as the entire Atom power budget to deliver that FLOP. Or perhaps it will, it's all just speculation at this point.
So that 32-core processor would deliver 16x32 = 512 FLOP/clock peak. I would guess that they could deliver a low-power part clocked at 1GHz judging by the efficiency of Intel's floating point units across the whole range (from Atom up to i7). That part would hit 512GFlop/s peak. Then it's just a guessing game of what clock-speed they could ramp it up to within that 300W TDP, 2Ghz? 3?
The real killer could be how much sustained throughput can be achieved on an x86 derivative. The Core-2 sustained throughputs were mental, but it used every OoO trick that Intel could throw at it. Without that advantage the peak:sustained ratio will be closer to AMD/Nvidia's current offerings.
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That's why you buy... 2 COMPUTERS! Where's the single string performance! Fuck more! Smaller, faster, Intel get on it!
wtf does the international school of amsterdam have to do with this?
To answer my own post, I'm not entirely sure about some of the facts. Like,... if I like the musty smell of men, does that mean I'm gay?
Chase the moment. Where does it go? Exactly.
I'm gonna go ahead and agree with management that maintainability is more important than any other factor. Having had to maintain a few ancient codebases is my day, I've seen way too many "clever" coders that do ridiculous tricks to save time or space. Well designed (read: maintainable) code does not imply any significant performance hit.
Like,... if I like the musty smell of men, does that mean I'm gay?
Either that, or you're French.
Unless you are interested in a pretty small class of problems, the inherent parallelism of most applications continues to be somewhere in the range 2.1 to 2.5 (i.e., you can speed them up by a little over 2x with the addition of more processors). Thus, in most real-world applications, most of those cores, or vector units, or any other "supercomputer" features will go unused.
If anyone here observes a quad-core chip running any particular load anywhere close to 4x the speed of a single core should write a paper about it, because this has been the holy grail of parallel computing for going on 40 years now.
That Intel thinks this is a solution is sadly typical -- the problem is a software one, not a hardware problem, and they do not know how to solve it.
As a former Cray employee I find it interesting to see that Intel's previously unannounced deal with Cray is finally starting to deliver the goods. Intel should just get it over with and buy Cray. They've wanted back into the supercomputer business for while now anyway.
Larrabee's support for Direct3D and OpenGL will determine its course of life. The reason is twofold. First, whether Larrabee-only games and applications (those that brig out the full functionality of Larrabee) get written will depend on its popularity. Second, for Larrabee to be adopted, it needs to support existing libraries like Direct3D and OpenGL. 1) The first part should be fairly obvious - it takes time to make a game or an application, so developers need to be invested to make one for Larrabee, which will not come to them until Larrabee has some share of the graphics-hardware market. 2) The second part is true because Larrabee-only games and applications do not exist yet. Consumers will not spend 200-300 dollars on a piece of hardware only because of its specifications. They will need to see its applications to buy it. And since no application with Larrabee in mind has been written yet, it will need to support existing applications, and they all use existing libraries such as Direct3D and OpenGL. Thus, Larrabee's success depends on its support for Direct3D and OpenGL, and Intel developers developing drivers for Larrabee will be responsible for it.
Awww how sweet. Henk has registered a name troll just for me. Poor guy, that's a lot of issues for such a sweet child to carry around.
Slashdot: where don knuth is an idiot because he cant grasp the awesome power of php
You don't have to use separate functions in C. C does have GOTO's, thank you very much :)
The subset of C enforced by many employers' coding standards lacks the goto keyword.
I'd be happy if someone could tell me a better way
If you can't get your boss to amend the coding standards to allow use of goto to handle exceptions in C, the better way involves leaving your employer. But that isn't practical in this recession.
I read all this multicore sales pitch as just whining about not being able to deliver faster cores in todays CPUs. Having a couple of cores at hand is nice on a deskop. Having four on a server is nice. But, most workloads arent easily ran on multiple cores. Virtualization wont have that much help from a 16 core chip since the I/O subsystem in a normal server will be long overused before the you have stressed an 8-way CPU to the max in most cases.
What we need is faster CPU-cores, not more of them. Since neither Intel nor AMD can deliver that they are trying their best making people believe what they really need is more cores and that the software people are the ones who has hit the wall. Its just an intricate blame-game where the real issue is that Mores law has slammed into a concrete wall in 200Mph. The upgrade threadmill is on the verge of slowing down and we cant have that can we?
HTTP/1.1 400
APL is the original matrix computing language, since morphed into J and K. Why handle just one number/character at a time? tOM
Epitaph: At last! Root access!
Until the hardware shows up at independent review sites and lives up to the rather over-the-top claims, this is all hype and FUD. As long as your current GPU provides 60fps on the games you want to play at your monitor's resolution, everything else means nothing.
"It's the height of ridiculousness to say for those 9 lines you get hundreds of millions."
>If Intel are smart they will release a chip containing one core (or 2 cores) from some kind of lower-power Core design and a pile of Larabee cores on the one die along with a memory controler
*Ahem*, what about memory bandwith??
One strong point of GPU is that they have big memory bandwith at a cheap cost as they use a fixed memory setup, if you put both the CPU and the GPU under the same memory controler with replaceable memory then it's quite likely that the GPU will suffer from the lack of memory bandwith.
I heard that Intel acquired some PowerVR IP, probably because tile-based rendering is set to use less memory bandwith than normal rendering, that said PowerVR's videocards were also less powerful than their competition..
Had MichaelSmith's post actually been modded Funny in those two and a half hours, I might have kept my post to 140 characters or less. But in some cases, goto increases speed (due to fewer variables spilled to the stack) without diminishing maintainability, and coding standards that exclude all uses of goto based on a misinterpretation of a 1968 article by Edsger Dijkstra are one of my pet peeves.
Retired? Really? Not a week ago. He may have given the CEO reins over to our favorite chair tosser, but he's still Chairman of Microsoft. No doubt his stock option package is quite good.
That's good for Microsoft, too. Three nines of companies don't long survive the loss of their founders. As Damon Runyon said, "The race may not always be to the swift, nor the battle to the strong, but that's the way to bet".
The fall may have even begun before he retired as CEO. When SCO's backstop with Baystar dried up, Microsoft lost all of its credibility in the smoke filled rooms where the real money makes deals. Who knows how much this cost RBC and the other partners? Gates will spend the rest of his life trying to make amends, but those who suffered will never forget. You can't swing a billion dollars without somebody dies, and the dead stay dead no matter how many soup kitchens you volunteer in afterward.
Eventually, pigeons come home to roost. The devil will have his due.
Help stamp out iliturcy.
95% of code doesnt need to be top notch in speed, but if your code otherwise is utter god slow, ie, do one operation take 12 minutes where another app takes 2 seconds, then you have some serious shit coders.
Also if your optimization/geewiz app takes 29hrs to run 24hrs of data, then its obviously not going to get any customers.
Point is, make it fast where it matters, not everywhere. Just look at itunes, is that written in javascript or quicktime scripting?
Document and document well if your doing tricky speed optimizations, or keep both slow and fast code together with a flag to run X or Y.
Liberty freedom are no1, not dicks in suits.
Surely they would just keep the instructions and translate them to run on Larrabee instead.
Does anyone else see the problem with this statement?
> [G]iven software that can parallelize across many such cores, performance can scale nearly linearly as more and more cores get packed onto chips in the future.
Perhaps this will help:
Given software that can catch a leprechaun, I will be rich in the future.