Thunderbolt 3 real speed: 21.6Gbps

Discussion in 'Mac Accessories' started by Mr Dobey, Feb 21, 2017.

  1. Mr Dobey macrumors 6502

    Aug 8, 2008
    In talks with both Sonnet Tech and Akitio, they have both independently told me that the real world speed of Thunderbolt 3 tops out at 21.6Gbps (2.7GBps) instead of the market 40Gbps. Even with a minor 3% hit from the 128b/130b encoding overhead of PCIe 3.0, these claims are about half of what is advertised. For whatever reason neither company will give a technical breakdown of why this is so.

    Has anyone here made a very fast setup such as RAID 0 of NVMe drives that could test this bandwidth claim over Thunderbolt 3?
  2. DRDR macrumors member

    Jul 23, 2008
    I am using a Thunderbolt 3 to Dual Displayport Adapter, driving two 4K displays. According to the Displayport standard this means the following data rate from one of my Thunderbolt 3 ports to the displays:

    2 x 12,96 GBit/s = 25,92 GBit/s

    This is the exact same data rate used when connecting a 5K display.
  3. MrX8503 macrumors 68020

    Sep 19, 2010
    That's not possible because the LG 5K is using the full 40Gbps.

    5K + 3x USB ports + webcam + speakers = ~40Gbps
  4. dyn macrumors 68030

    Aug 8, 2009
    Did they also tell you how they tested it and what they used for the test? Without knowing that it's just throwing out numbers which says absolutely nothing at all.

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3 February 21, 2017