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MSI Calls Bluff on Gigabyte's PCIe Gen 3 Ready Claim

Discussion in 'News' started by btarunr, Sep 7, 2011.

  1. Ultim8 New Member

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  2. neliz

    neliz

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    If you read the presentation, you also see the other components that need be used besides the switches.
    You can't just expect a 5 GT/s circuitry to handle 8GT/s data without issues.


    I fail to see how you can not do a complete ROM reflash on any mainboard and require a dual bios for this since it's pretty much standard business in the server world.

    Unless of course, one certain company that likes to promote dual bios'es on their boards would tell the press that "it might" and "it could" to make people afraid.


    Yes, or a simple Gen3 card with test chip.
     
    Last edited: Sep 8, 2011
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  3. Ultim8 New Member

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    Neliz it does, The controller is on the cpu.

    For multi gpu yes you need PCIe3 switches for the bridge but Gigabyte have given all there 6 series pci gen3 for the first slot at least.
     
  4. RuskiSnajper

    RuskiSnajper

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    HAHAHA lol big win for MSI PR .... what a good oportunity taken for some technical explanation which might not only win over people to buy msi boards but also make better company image

    shame on you gigabyte ... would expected it to be asus
     
  5. neliz

    neliz

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    Let me make this VERY clear for you. in a LOT of these boards, data travels through the PCI express switches as it NEEDS TO.
    Otherwise it's impossible to switch the first slot between x16 and x8.

    [​IMG]
     
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  6. Ultim8 New Member

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    Only if you use the 2nd slot, if you dont use the 2nd slot you dont need the switch.....then there is no bottle neck. Get it.
     
  7. neliz

    neliz

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    Sorry, but if you don't know the first thing about how a Sandy Bridge CPU switches between 16/0 and 8/8 and why the switch chips are there and how the traces work. .I'll need to use mspaint to draw pictures. HOLD ON! :)
     
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  8. jfk1024

    jfk1024 New Member

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    The physical links are the same. So... i know you need a new physical link for every new coding, but you can also use the same physical link to transfer different encoded data.
     
  9. neliz

    neliz

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    you're talking about PCI Express 2.1 then? Which, with 128/130 encoding has exactly the same BW as PCI Express 2.0?
     
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  10. Ultim8 New Member

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    lol.

    Right the pcie controller is on the cpu do you agree?

    So if the controller is on the cpu and the traces are identical (They are) then why wont a single graphics card work at 16x gen3?

    The switch is only used one a 2nd gpu is inserted
     
  11. neliz

    neliz

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    PCI Express switching 101:

    On top the CPU
    8 PCIe lanes go the the first slot
    8 PCIe lanes go the the 4 PCI express switches
    If no card is detected in the second slot, all traffic will go to slot 1
    The clock gen for the second PCIe card is actually housed in the PCH/southbridge

    The only way to do 8/8 is by having switches and a setup like in the picture below
    NO switches, IE all 16 lines are going straight from the CPU to the first slot results in 16/4 setups for crossfire for instance.

    [​IMG]
     
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  12. n-ster

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    I never said GB did or did not lie, I was just showing the UD7 thing that the other was talking about.

    I might sound stupid, but...

    [​IMG]

    PCI-E 2.X is 5GT/s, but with the overhead, it is actually closer to 4GT/s, so 16 lanes of 2.X should be equivalent to 8 lanes of PCI-E 3.0 no?
     
  13. jfk1024

    jfk1024 New Member

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    let's just wait until the ivy bridge and pci-e 3.0 gpu are released. Until then, It's just speculation.
     
  14. Ultim8 New Member

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    Exactly so the first slot will be gen3 x16 as long as the other pcie lanes are not occupied.
    This is what i said from the beginning
     
  15. cadaveca

    cadaveca My name is Dave

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    But that is not possible. what will happen is that the primary slot will only get x8 link that is PCIe 3.0, and the other 8 lanes will not be capable of 3.0 due to the board's hardware in the link. This may create situation where the slot defaults to PCIe 1.0, or perhaps 2.0, because of the lane confusion.


    TBH, I'm not sure, exactly, what will happen with these boards and the primary slot. It's not as simple as it seems.
     
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  16. neliz

    neliz

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    The first slot is X16 because they go through the PCI express switches :) so they ARE NOT GEN3 :)

    I've highlighted it on a gigabyte board so you can see where the lanes are coming from.

    [​IMG]
     
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  17. Ultim8 New Member

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    PCIe3 8 will be faster as 128/130 encoding is ~1.5% loss
     
  18. Ultim8 New Member

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    But Neliz even from that diagram the PCIe switches are only touched or needed when a second pcie device is installed???
     
  19. [H]@RD5TUFF

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    Exactlly there you really can't trust either, but I trust Gigabyte the least.
     
  20. neliz

    neliz

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    I think it will :p


    No! :)

    How to calculate PCI Express bandwidth:
    Transfer rate * encoding

    PCI Express Gen2:
    Transfer rate: 5GT/s = 5000 Gb/s = 625 GB/s
    625 * 8/10 (encoding) = 500 MB/s
    PCI Express = Full duplex, so total bandwidth = 500*2 = 1GB/s

    16 lanes*1GB/s = 16GB/s

    PCI Express Gen3:
    Transfer rate: 8GT/s = 8000Gb/s = 1000 GB/s
    1000 * 128/130 = 984.6154 GB/s
    PCI Express = Full Duplex, so total bandwidth = 984.6154 * 2 = 1969.2308
    8 lanes *1969.2308GB/s = 15753.8464 GB/s

    No, PLEASE, check the picture:

    You can see that only 8 lanes are connected to the CPU (on top) the other 8 lanes come from the PCI express switches.
    If you have a good high res picture of a board you can actually SEE the traces from the switch to the slot.

    [​IMG]
     
    Last edited: Sep 8, 2011
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  21. jfk1024

    jfk1024 New Member

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    Do you believe yourself saying that?
     
  22. neliz

    neliz

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    Yes, do you have any reason to doubt?
    Please prove me wrong because I hate it when I make big mistakes in public :)
     
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  23. jfk1024

    jfk1024 New Member

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    when the second pci-e slot is NC the SW is OFF so all the PCI-e lanes are directly connected to the CPU.
     
  24. n-ster

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    so PCI-E 2.X x16 is faster than PCI-E 3.0 x8... So speed-wise, PCI-E 2.X x16 is already pushing PCI-E 3.0 bandwidth, although in an 8 lane configuration
     
  25. neliz

    neliz

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    No because I just showed in the picture above that only 8 lanes are directly connected to the CPU, the other 8 lanes COME FROM THE SWITCH.

    If you can show me a pericom switch that has a supersecret awesomemode where it magically transforms from a 5GT/s switch to a 8GT/s passive transceiver, you've got me convinced.
    Otherwise, I have NO idea where you get your information from that the Gen2 switches can turn themselves of and do some mystical rerouting.

    Gigabyte's wording was "Gen3 maximum bandwidth" which would be 32GB/s not 16GB/s
     
    Last edited: Sep 8, 2011
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