How Many Cores in a Larrabee?

Initial estimates put Larrabee at somewhere in the 16 to 32-core range, we figured 32-cores would be a sweetspot (not in the least because Intel's charts and graphs showed diminishing returns over 32 cores) but 24-cores would be more likely for an initial product. Intel however shared some data that made us question all of that.

Remember the design experiment? Intel was able to fit a 10-core Larrabee into the space of a Core 2 Duo die. Given the specs of the Core 2 Duo Intel used (4MB L2 cache), it appears to be a 65nm Conroe/Merom based Core 2 Duo - with a 143 mm^2 die size.

At 143 mm^2, Intel could fit 10 Larrabee-like cores so let's double that. Now we're at 286mm^2 (still smaller than GT200 and about the size of AMD's RV770) and 20-cores. Double that once more and we've got 40-cores and have a 572mm^2 die, virtually the same size as NVIDIA's GT200 but on a 65nm process.

The move to 45nm could scale as well as 50%, but chances are we'll see something closer to 60 - 70% of the die size simply by moving to 45nm (which is the node that Larrabee will be built on). Our 40-core Larrabee is now at ~370mm^2 on 45nm. If Intel wanted to push for a NVIDIA-like die size we could easily see a 64-core Larrabee at launch for the high end, with 24 or 32-core versions aiming at the mainstream. Update: One thing we did not consider here is power limitations. So while Intel may be able to produce a 64-core Larrabee with a GT200-like die-size, such a chip may exceed physical power limitations. It's far more likely that we'll see something in the 16 - 32 core range at 45nm due to power constraints rather than die size constraints.

This is all purely speculation but it's a discussion that was worth having publicly.

Putting it all Together - Return of the Ring Bus Cache and Memory Hierarchy: Architected for Low Latency Operation
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  • erikespo - Monday, August 04, 2008 - link

    http://en.wikipedia.org/wiki/Square_%28geometry%29">http://en.wikipedia.org/wiki/Square_%28geometry%29

    helpful page to take you back to first grade

    and excuse my decimal point.. it is 204.49mm total per core or 14.3mm^2
    Reply
  • erikespo - Monday, August 04, 2008 - link

    Explain.

    lets use smaller numbers for you 2mm^2 is 2mm by 2 mm or 4 total mm

    double that and it is 4mm^2 or 4 mm by 4 mm or 16mm total..

    we are talking about area or 2 dimensions not 1 dimension.

    Same math applies to the article
    Reply
  • MamiyaOtaru - Monday, August 04, 2008 - link

    No, you're way off. 2mm² is TWO square millimeters. (a rectangle 1x2 for example). Double that would be 4mm², which could either be 1x4 or 2x2.

    NUMBERmm² doesn't mean NUMBERxNUMBER mm, it means exactly what it says: NUMBER mm².

    Using your smaller numbers: 2mm² is not "4 total mm"; it is TWO mm². Saying it is 4 total mm doesn't even make sense. You _can't_ measure area in millimeters. You measure it in square millimeters, and there are two of them (_2_mm²).

    Here's an mspaint visual (if links work: http://img105.imageshack.us/my.php?image=squaremma...">http://img105.imageshack.us/my.php?image=squaremma...

    You're so sure you're right on this, it's really depressing :(
    Reply
  • darkequitus - Monday, August 04, 2008 - link

    I did not appriciate the writer creaming over every digital page they wrote. especially when Larrabee's performance is mainl at the moment based on INtel hype and nothing real. Reply
  • ZootyGray - Monday, August 04, 2008 - link

    THANK YOU.

    Somebody finally said it.

    The others prefer Eutopian illusion - aka the curse aka ntel antitrust. ntel has no grafx and the fools in the public buy "inside' and nvid and ati aren't exactly friends of the curse.

    welcome to the matrix. wakey wakey
    Reply
  • ZootyGray - Monday, August 04, 2008 - link

    and a 16 pager on maybe might could be should be = wannabe "employ-boy"
    - payday ? hooyeh. This is so disappointing for me. Credibility sags to a new low.
    Reply
  • strikeback03 - Tuesday, August 05, 2008 - link

    Someone whose two posts contain about 10 complete words and no complete thoughts says Anandtech's credibility has sagged to a new low? Reply
  • ZootyGray - Tuesday, August 05, 2008 - link

    haha yeh - lots of room for thinking.
    or - if no thinkeez - ya gots der 16 pg inundation (that's a big word like marmalade) all based on nothing-is-real - you like that kind of brainwash? we don't know anything; but here's the tekspex?
    btw - did u get it? the matrix idea? watch the movie. cos here it is. pardon my loaded cryptic literacy.
    thx
    if you don't get it - well, that's what they want - a world of sleeping mob. never mind, that's just my concern.

    Reply
  • The Preacher - Monday, August 04, 2008 - link

    I don't really care about how good it will be executing some software renderer but I feel it is going to kick ass in scientific calculations. Matrix operations, FFT/convolution, tremendous bandwidth, double precission... I may write C++/x86 assembly code directly for it and I may put this into a rack of servers and use it through MPI. Give me a compiler with vector intrinsic functions for it and my dreams just came true! :) Reply
  • elerick - Monday, August 04, 2008 - link

    I have been a daily reader of another hardware review site for years. I ready nearly every articles that headlines and find many of them quite lacking. Today I got wind of your review for the Larabee. It was very well written and produced an amazing amount of tech knowledge not really commonly reviewed. I'm glad to have found you this site, and I never create an account but today I felt obligated to. Great work.

    PS: any news on that AMD / Fusion? or is that just them being intimidated by Intel's Larrabee?
    Reply

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