Retina MBP's 2 Thunderbolt Ports

Discussion in 'MacBook Pro' started by ///KM, Jun 12, 2012.

  1. ///KM macrumors member

    Sep 3, 2009
    Anyone have any information on the 2 Thunderbolt ports on the RMBP, specifically: is it 2 x 10Gbps ports on 2 PCIe connections, or do the 2 ports share a 10Gbps PCIe connection, effectively halving the bandwidth if the two ports are in use?

    Apple's specs are unclear: "Two Thunderbolt ports (up to 10 Gbps)"
  2. Moriarty macrumors 6502

    Feb 3, 2008
    I don't know how the PCI-Express bus design has changed with the new processors. But on the 2011 iMac, there is only one 20 Gbps PCI-E bus, which the two Thunderbolt ports share. I suspect the new Pro is the same.

    It's a poorly publicised limitation that could have consequences for a select few people... but Apple should say more about it nevertheless so people running lots of high end I/O and displays don't run out of bandwidth (that could cause much more nasty problems than say just having lots of USB devices on a hub hogging bandwidth, I suspect).
  3. Stetrain, Jun 12, 2012
    Last edited: Jun 12, 2012

    Stetrain macrumors 68040

    Feb 6, 2009
    This most likely uses the brand new Cactus Ridge controller for Thunderbolt:

    So it looks like four 10GB lanes, two per port. Basically double the usable bandwidth of the previous gen MBP.

    Edit: It may also use the previous gen Light Ridge controller which has similar specs:
  4. ///KM thread starter macrumors member

    Sep 3, 2009
    Thanks mate :) I guess we'll find out which controller is in use once iFixit does their teardown and/or Anandtech publishes their review.
  5. Stetrain macrumors 68040

    Feb 6, 2009
    As far as I can tell there isn't any real difference in features and performance between them, just physical size and cost.
  6. ///KM thread starter macrumors member

    Sep 3, 2009
    According to the iFixit teardown, looks to be the DSL3510L Cactus Ridge controller :) I hope this means both ports get the full 10Gbps, double the bandwidth!
  7. Erasmus macrumors 68030


    Jun 22, 2006
    Hiding from Omnius in Australia
    I believe both ports should be able to run at 20 Gbit/s, as they are both dual channel 10 Gbit/s.

    I still don't really understand how Thunderbolt works, but I am assuming that each port contains one 10Gbit/s PCIe lane, and another lane that can either operate as a second 10Gbit/s PCI lane, or DisplayPort.

    Wondering how long it takes companies to start developing external PCIe housings that can take all four thunderbolt lanes, and connect them to two high end desktop GPUs in Crossfire/SLI...

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