If "Negotiated Link Speed" is lower than "Link Speed"..?

Discussion in 'MacBook Pro' started by lip5016, Sep 24, 2014.

  1. lip5016 macrumors regular

    Joined:
    Jul 11, 2014
    #1
    From my "About This Mac":

    Intel 6 Series Chipset:

    Vendor: Intel
    Product: 6 Series Chipset
    Link Speed: 6 Gigabit
    Negotiated Link Speed: 3 Gigabit

    Physical Interconnect: SATA
    Description: AHCI Version 1.30 Supported

    What does "Negotiated Link Speed" mean?
    Does that mean that this drive listed above will only run at 3 Gigabit, and not the full 6 Gigabit?
     
  2. prisstratton macrumors 6502

    prisstratton

    Joined:
    Dec 20, 2011
    Location:
    Winnipeg
    #2
    Seeing as you listed 2 x SSD, I am guessing that you put one in the opti-bay and this is the one you are referring to. If that is the case then your model MBP does not support (reliably.....according to OWC) 6 Gigabit in that location.
     
  3. simonsi macrumors 601

    simonsi

    Joined:
    Jan 3, 2014
    Location:
    Auckland
    #3
    Correct. You are connected at 3G even though the link controller chip supports 6G.
     
  4. lip5016 thread starter macrumors regular

    Joined:
    Jul 11, 2014
    #4
    Really weird. Somehow after installing OSX on the 2nd disk, it became 6G across the board for everything.. go figure lol
     
  5. simonsi macrumors 601

    simonsi

    Joined:
    Jan 3, 2014
    Location:
    Auckland
    #5
    There are various conditions that will cause the link speed to be renegotiated (power off/on is the obvious one), it will likely also periodically attempt to renegotiate higher if seeing no transmission errors across the interface, as well as negotiate down if it does see errors. "Periodically" could be data-volume based so if you moved 20GB (say) installing the OS then that may have caused an in-flight renegotiation of the link speed.

    If it continues to fluctuate 3G-6G-3G then it might be worth replacing the interface cable to see if that improves the link quality. Equally if you can't tell in usage if the speed steps down, it may not be worth worrying about :cool:
     

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