Is the issue with TB3 fixed in 2017 nTB MBP?

Discussion in 'MacBook Pro' started by ghanwani, Jun 18, 2017.

  1. ghanwani, Jun 18, 2017
    Last edited: Jun 19, 2017

    ghanwani macrumors 6502a

    Dec 8, 2008
    (Edit: Apologies for the incorrect subject line. This relates to TB, not nTB.)

    There was an issue which required lower speed on 2 out of the 4 Thunderbolt 3 ports in the 2016.

    Is the issue addressed in the 2017 models?
  2. PieTunes macrumors 6502


    May 6, 2016
    San Diego, CA
    No, the two ports on the right side still have reduced PCI Express bandwidth than the two on the left. This is only on the 13" model. Something technical to do with the chipset, implementation of the TB controller, etc. If someone knows the specific reason, I'm sure they will chime in.
  3. killawat macrumors 65816

    Sep 11, 2014
    Dual Core Skys and Kabys have 12 Lanes PCIE while Quad Core has 16. No conspiracy here, simply not enough bandwidth on the dual core 13" chips to support 40 Gbits on the the two ports.
  4. Shamgar macrumors regular

    Jun 28, 2015
    The reports I've heard indicate that the restriction was due to PCIe lanes on the CPU itself. Each pair of ports is run from a single Thunderbolt controller. The left side has a full x4 PCIe link for the controller, while the right side has a x2 link (basically equivalent to Thunderbolt 2 in bandwidth).

    What I've been trying to figure out is what the exact restriction is. I think it's a limitation of lane configurations that Intel has made available. The dual core chips have 12 lanes, which should be enough, but from the best I can parse their documentation, they only make a single x4 link available in any configuration. By comparison, the quad cores in the 15" have 16 lanes, which use x8 for the GPU, and then 2x4 for the Thunderbolt controllers.
  5. ghanwani thread starter macrumors 6502a

    Dec 8, 2008

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