XPS 15 9550 not negotiating TB3?

Discussion in 'Dell XPS and Studio XPS' started by Splitframe, Dec 9, 2016.

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  1. Splitframe

    Splitframe Notebook Guru

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    Hi,

    I am using a Thunder3 enclosure with a GPU and noticed that it only
    negotiates an x2 Gen3 link instead of an x4 Gen3 link.
    Now I know that the Thunder3 does not support GPUs so I borrowed
    the Samsung 960 Pro SSD from a friend to verify.
    The read values I got were only around 1500 MB/s instead of the
    over 3000 MB/s I get on a Desktop.

    I don't know if the issue is with the XPS 15, the Thunderbolt cable or the Thunder3
    directly. I have no other Thunderbolt 3 enabled device to check.

    All Firmwares and Driver are the newest I could find. The Dell BIOS is from the 1st December even. Only the NVidia driver is one release old because the newest only negotiated an x2 Gen2 link.

    Most tools like GPU-Z report a x4.3 link, but the performance shows that it's not. Maybe they only see
    how the Thunderbolt Controller is connected. The NVidia system information seems to be more reliable.

    http://imgur.com/a/CIBQJ
     
  2. kent1146

    kent1146 Notebook Prophet

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    If it helps, the difference in pcie bandwidth won't make much of a difference in GPU performance.
     
  3. kent1146

    kent1146 Notebook Prophet

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    And it is possible that you may be using a sub-quality cable?

    Are you using a regular USB TypeC cable, or a cable specifically spec'ed for Thunderbolt 3?

    They are compatible cables, but some USB Type C cables are of high enough quality to negotiate full Thunderbolt 3
     
  4. Splitframe

    Splitframe Notebook Guru

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    I use the 50cm TB3 Cable that came with the AKiTiO.
     
  5. Eason

    Eason Notebook Virtuoso

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    Hmm maybe they're not using an active cable? Is it 20gbps or 40? Most 50cm should be 40.
     
  6. Splitframe

    Splitframe Notebook Guru

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    I was in contact with AKiTiO and they said they only had a XPS 13 9350 to test and that
    the XPS 13 is indeed only connected with a x2.3 link and that the HWInfo64 screenshot ( look below )
    looks exactly the same on my XPS 15 as on their XPS 13.

    The XPS 15 in advertised in germany as "Enjoy up to 40GB/s with Thunderbolt 3", but if the above is true
    there is no chance of ever reaching this speed...

    [​IMG] [​IMG]
     
  7. ChanceJackson

    ChanceJackson Notebook Evangelist

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    sounds like class action lawsuit time to me
     
  8. _sem_

    _sem_ Notebook Deity

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    AFAIK it's been a while since this was found. You can enjoy 40Gbps with TB3 if you connect two displays DP 4K@60Hz (and it happens to work) - in this case a 4x PCIe link would get throttled because 40Gbps wouldn't do. But unfortunately it is only 2x, including the 9560.
     
  9. Splitframe

    Splitframe Notebook Guru

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    About the 40Gbit/s, I meant you can never reach 40Gbit/s bi-directional, because PCIe and USB are the only bi-directional protocols ( aside from some monitor info/sync from the monitors )
    implemented in TB3. So you can send out 40 with DP, but only receive 20/16.

    Aside from that, what do you mean with "AFAIK it's been a while since this was found."?
    This post is from the 9th December, I dare to say I was the first to notice that the 9550 was only connected with two PCIe lanes,
    because I remember doing a thorough search beforehand.
     
  10. _sem_

    _sem_ Notebook Deity

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    Sorry meant to reply to the post reviving the thread.
     
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