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x86: The Right Choice?

Larrabee: Intel's New GPU

We might tend to forget this additional cost of several hundred thousand transistors today, when modern processors have several hundred million transistors, but if you go back in time 15 years ago when the Pentium and PowerPC 601 were in rivalry, Intel’s latest processor used approximately 15% more transistors than IBM’s did. And a difference of 500,000 transistors when the entire processor had approximately three million is far from negligible. So did economic factors run counter to good technological sense? Not really.

First of all, Intel has the benefit of 30 years of expertise with its x86 architecture, and even if it does possess skills with VLIW (IA64) and even RISC (i860, i960) architectures, its experience with the x86 architecture is a genuine advantage. Obviously, that experience is with hardware as well as software, since Intel can re-use its years of research on x86 compilers.

A second point is that the choice of CISC has advantages as well as disadvantages. while RISC instructions are of similar size and constructed in the same way to make decoding easier, CISC instructions are of variable size. Also, while decoding is complicated, x86 code is traditionally more compact than the equivalent RISC code. Here again you might tend to think that factor is negligible, but in this case, these are processors with very small caches, where every kilobyte counts.

The choice of the x86 has one more advantage: it’s an opportunity for Intel to re-use one of its older designs, which is exactly what the engineers did. Intel’s last in-order processor was the Pentium MMX (P55), but the improvements it made over the classic Pentium (the P54C) weren’t really worthwhile in the context of the Larrabee project. It made more sense to use the original. But here again a question arises: Wouldn’t it have made more sense to start from scratch and design a processor that was perfectly suited to Larrabee?

There’s a tenacious myth in the public’s mind associated with starting with a clean slate when it comes to processor designs, which is seen as synonymous with quality. Most people see it as an opportunity to get rid of all the encumbrances of the past. But in practice, it’s extremely rare for engineers to start from scratch. First of all, because there’s no point in it. Many building blocks are perfectly reusable and don’t need to be created all over again. Also, it would be too expensive in terms of time and money.

While Intel undeniably knows how to design and produce x86 processors, we tend to forget the amount of time it takes to completely debug a design. Obviously, famous bugs like the Pentium floating-point division bug or Phenom Translation Lookaside Buffer (TLB) come to mind because they made headlines. But in fact, all processors have bugs of varying significance. All you need to do is read the manufacturers’ data sheets that list them for a certain processor model. The advantage of modifying an existing design like the Pentium is that it has already been extensively tested and debugged, which is a great head start. Insider rumors say that Intel has re-used the Pentium design that the Pentagon carefully modified when it was used for military purposes. That’s not very credible, but it adds to the Larrabee mystique, and Intel will likely not deny it.

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  • 0 Hide
    thepinkpanther , March 23, 2009 6:35 AM
    very interesting, i know nvidia cant settle for being the second best. As always its good for the consumer.
  • 6 Hide
    IzzyCraft , March 23, 2009 6:49 AM
    Yes interesting, but intel already makes like 50% of every gpu i rather not see them take more market share and push nvidia and amd out although i doubt it unless they can make a real performer, which i have no doubt on paper they can but with drivers etc i doubt it.
  • 0 Hide
    Anonymous , March 23, 2009 6:50 AM
    I wonder if their aim is to compete to appeal to the gamer market to run high end games?
  • 0 Hide
    Alien_959 , March 23, 2009 8:12 AM
    Very interesting, finally some more information about Intel upcoming "GPU".
    But as I sad before here if the drivers aren't good, even the best hardware design is for nothing. I hope Intel invests more on to the software side of things and will be nice to have a third player.
  • 0 Hide
    crisisavatar , March 23, 2009 8:28 AM
    cool ill wait for windows 7 for my next build and hope to see some directx 11 and openGL3 support by then.
  • 0 Hide
    Stardude82 , March 23, 2009 8:32 AM
    Maybe there is more than a little commonality with the Atom CPUs: in-order execution, hyper threading, low power/small foot print.

    Does the duo-core NV330 have the same sort of ring architecture?
  • 2 Hide
    liemfukliang , March 23, 2009 10:27 AM
    Driver. If Intel made driver as bad as Intel Extreme than event if Intel can make faster and cheaper GPU it will be useless.
  • 3 Hide
    IzzyCraft , March 23, 2009 10:44 AM
    Hope for an Omega Drivers equivalent lol?
  • 1 Hide
    phantom93 , March 23, 2009 11:16 AM
    Damn, hoped there would be some pictures :( . Looks interesting, I didn't read the full article but I hope it is cheaper so some of my friends with reg desktps can join in some Orginal Hardcore PC Gaming XD.
  • 9 Hide
    Slobogob , March 23, 2009 11:51 AM
    I was quite suprised by the quality of this article and am quite eager to see the follow up.
  • 1 Hide
    JeanLuc , March 23, 2009 12:26 PM
    Well I am looking forward to Larrabee but I'll keep my optimisim under wraps until I start seeing some screenshots of Larabee in action playing real games i.e. not Intel demo's.

    I wonder just how compatible larrabee is going to be with older games?
  • 3 Hide
    tipoo , March 23, 2009 12:46 PM
    Great article! Keep ones like this coming!
  • -2 Hide
    tipoo , March 23, 2009 12:48 PM
    IzzyCraftHope for an Omega Drivers equivalent lol?

    That would be FANTASTIC! Maybe the same people who make the Omega drivers could make alternate Larrabee drivers? We all know Intel sucks balls at drivers.
  • 7 Hide
    armistitiu , March 23, 2009 12:49 PM
    So this is Intel's approach to a GPU... we put lots of simple x86 cores in it , add SMT and vector operations and hope that they would do the job of a GPU. IMHO Larrabee will be a complete failure as GPU but as an x86 CPU that is highly parallel this thing could screw AMD's FireStream and NVIDIA's CUDA (OPENCL too) beacause it's x86 and the programming is pretty popular for this kind of architecture.
  • 0 Hide
    wicko , March 23, 2009 1:18 PM
    IzzyCraftYes interesting, but intel already makes like 50% of every gpu i rather not see them take more market share and push nvidia and amd out although i doubt it unless they can make a real performer, which i have no doubt on paper they can but with drivers etc i doubt it.

    Yeah but that 50% includes all the integrated cards that no consumer even realizes they're buying most of the time.. but not in discrete cards. I'd like to see a bit more competition on the discrete side.
  • 2 Hide
    B-Unit , March 23, 2009 1:26 PM
    wtfnl"Simultaneous Multithreading (SMT). This technology has just made a comeback in Intel architectures with the Core i7, and is built into the Larrabee processors." just thought i'd point out that with the current amd vs intel fight..if intel takes away the x86 licence amd will take its multithreading and ht tech back leaving intel without a cpu and a useless gpu

    Umm, what makes you think that AMD pioneered multi-threading? And Intel doesnt use HyperTransport, so they cant take it away.
  • 1 Hide
    justaguy , March 23, 2009 2:02 PM
    Now we know what they're trying to do with it. There's still no indication if it will work or not.

    I really don't see the 1st gen. being successful-it's not like AMD and nVidia are goofing around waiting for Intel to join up and show them a real GPU. Although there's no numbers on this that I've seen, I'm thinking Larry's going to have a pretty big die size to fit all those mini-cores so it better perform, because it will cost a decent sum.
  • 8 Hide
    crockdaddy , March 23, 2009 2:09 PM
    I would mention ... "but will it play crysis" but I am not sure how funny that is anymore.
  • -4 Hide
    Pei-chen , March 23, 2009 2:12 PM
    Can't wait for Larrabee; hopefully a single Larrabee can have the performance of 295. Nvidia and ATI are slacking as they know they can price fixing and stop coming out with better GPU, just more cards with the same old GPU.
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