Why no odd number of intel cpu

Discussion in 'Newbie Lounge' started by lt_matthew, Apr 6, 2021.

  1. lt_matthew

    lt_matthew Member

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    After reading the reviews of rocket lake I was thinking why didn't intel have a 7 or 9 core cpu in its line up. (Not the ridiculous amount of cpus that are slightly different, though 9 cores might be pushing it). It makes more sense than adding the avx 512 function (does that take up valuable real estate on the cpu).
    I'm assuming its because the equivalent amd cpu performs better.
    The whole situation got me thinking why are cpu all even number. I know because of amd chipset arrangement it makes sense to be even but since intel cpu are mono die I see no reason why.
    Also if rocket lake wasn't such a obvious stop gap, I would argue that intel should have implemented the hybrid approach of mixing low power cpu with desktop cpu to avoid the heat and power issues with rocket lake. Also would have given them the chance to work out any bugs. I'm assuming it was delays and cost over runs.
     
  2. wwwww

    wwwww Member

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    A majority of Intel CPUs have an odd number of cores. From memory they didn't even have an even-numbered core CPU until 2005 or so.
     
  3. theSeekerr

    theSeekerr Member

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    The answer is mostly boring: Rectangles and symmetry. Cores need access to shared resources, like cache, and that's most efficiently achieved by mirroring them either side of the shared resource. Here's what a quad-core Intel looked like a couple generations ago:

    [​IMG]

    Historically AMD did have some 3 core models - they were manufactured as 4 core dies but had one core that didn't pass all the tests, so they disabled the core and sold it as a cheaper CPU. Every manufacturer still practices "binning" of CPUs based on the tests they pass and how well each chip performs - you can see a very obvious example in the new Apple M1 chips, where the cheapest Macbook Airs have a 7 core GPU instead of the full 8 enabled cores on the higher models.
     
  4. OP
    OP
    lt_matthew

    lt_matthew Member

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    Thanks for the replies.
    Now that you mention it I remember reading there was a hack where you could turn on the disabled amd core. Is this true and was it worth while, I assume so as you would get a free core.
     
  5. theSeekerr

    theSeekerr Member

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    Yeah, it was true, and often worthwhile. In the early days the cores were usually disabled for a reason (errors/instability/temperatures) but when the yields improved the 3-core chips often had nothing wrong with them, just a disabled core to have an offering to sell at that price point.

    And then Sandy Bridge came out and AMD fell behind until Ryzen, so nobody cared.
     
  6. Renza

    Renza Member

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  7. theSeekerr

    theSeekerr Member

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    lt_matthew

    lt_matthew Member

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    Thanks for the diagram Seekerr. I might be taking a wild guess but if the new ice lake cpu are arranged similar to the above I can see how you could benefit from a high and lower power cpu array. Especially if you could run them at different frequencys.
     

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