5K iMac Thunderbolt ports

Discussion in 'iMac' started by 4God, Sep 6, 2015.

  1. 4God macrumors 68020

    4God

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    #1
    Are the 2 Thunderbolt 2 ports on the 5K iMac on the same bus or separate? (sorry if this has been asked and answered already, I searched but couldn't find anything)
     
  2. matreya macrumors 65816

    matreya

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    Nov 14, 2009
    #2
    Separate. I have 6 devices attached to one port and 3 attached to the other...
     
  3. 4God thread starter macrumors 68020

    4God

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    #4
  4. matreya macrumors 65816

    matreya

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    #5
    If it's the same bus, how can you have 12 devices to connected to it? I currently have 9 devices connected... I thought a single bus would be limited to 6 devices?
     
  5. 4God thread starter macrumors 68020

    4God

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    #6
    Good question, I thought it was per port but you might be on to something. Hopefully someone can chime in to explain. I would like to use 2 RAID0 setups on each port to combine them as one.
     
  6. matreya macrumors 65816

    matreya

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    #7
    What kind of RAID0 setups are you trying to combine?
     
  7. DeltaMac macrumors 604

    DeltaMac

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    #8
    I think that the System Information window/Thunderbolt will show you how those devices are connected.
    If there is more than one bus (with 9 devices, then the device tree will show that.
    I expect that you have more buses available, if some or all of your devices are attached through a Thunderbolt dock.
    But the internal hardware has only one bus available.
    And, the device tree will make that clear.

    Does any Mac other than the nMP have more than one TB bus?
     
  8. 4God thread starter macrumors 68020

    4God

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    #9
    I have a pair of 4TB RAID0 that I would like to make into one 8TB RAID0 but it would require them to be on a separate bus to work efficiently/correctly.
     
  9. matreya macrumors 65816

    matreya

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    #10
    Not really, because the bandwidth is more than sufficient to handle 4 hard drives in RAID0. I actually have 4 x 2TB Toshibas in RAID0 inside an OWC Thunderbay IV and BlackMagic benchmarks at around 720MB/sec peak.
     
  10. g4cube macrumors 6502a

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    Apr 22, 2003
    #11
    Explanation: The THunderbolt2 controller is a Falcon Ridge controller. It connects to the PCIe 2.0 bus using 4-lanes and provides 2 Thunderbolt ports.

    For example, the Mac Pro provides 6 Thunderbolt ports, using 3 Falcon Ridge controllers.

    When Alpine Ridge Thunderbolt3 controllers come into use, there will still only be 4 PCIe lanes used and 2 Thunderbolt3 ports provided. The increased speed comes from the PCIe 3.0 bus.

    More info here for Thunderbolt2:
    http://www.anandtech.com/show/7049/intel-thunderbolt-2-everything-you-need-to-know
     
  11. 4God thread starter macrumors 68020

    4God

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    #12
    Right, but that's probably in one enclosure. I have 2 enclosures that each have 2 drives (2TB each) to make the 4TB RAID0. I want to access both enclosures as one 8TB RAID0. I don't think daisy chaining the 2 enclosures would work as expected hence the desire for two separate buses.
     
  12. g4cube macrumors 6502a

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    Apr 22, 2003
    #13
    You'll find on iMac that performance would be same either daisychained or one into each port. With right drives, you could get up to 1.3GB/sec on your iMac.

    That's what you can get with one LaCie Little Big Disk, RAID-0, across 2 PCIE SSDs.

    Other than "fast", what performance do you really need?
     
  13. dyn macrumors 68030

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    #14
    Has little to do with PCIe and all to do with the available channels in the Thunderbolt protocol. Thunderbolt 1 and 2 don't differ that much. The only reason why TB2 is faster is because it is able to aggregate channels. Both TB1 and 2 have 4 channels in total, 2 per port and each channel is able to do 10Gb/s. If you aggregate all the channels of 1 port you get a bandwidth of 20Gb/s (that's why the System Profile screenshot reports "10Gbit/s x2" and "10Gbit/s x1").

    In case of TB3 things are quite different as there are a lot of changes. PCIe 3 is one of them and should be the main component that increases the speed.

    For those of you wondering, the amount of devices is per port, so max 6 per port. In case of the iMac that means a total of 12 devices (2x6). If you need more ports you need additional controller(s) like the Mac Pro (it uses 3 controllers to provide 6 ports).
     
  14. g4cube macrumors 6502a

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    Apr 22, 2003
    #15
    Yes and no.

    You are correct regarding the Thunderbolt side of things. I was referring to the PCIe side of things, max bandwidth and lanes used to communicate with the CPU.
     
  15. dyn macrumors 68030

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    #16
    In that case your reply is completely offtopic here and only causing confusion. The question is about Thunderbolt ports which are connected to the Thunderbolt controller. How the controller is connected to the rest of the machine and how the rest of the machine interacts with it (and vice versa) doesn't matter in this case. The Thunderbolt ports do not speak any other language than Thunderbolt. It is the controller that will have to speak the other languages (DisplayPort, PCIe and later on USB3.1). The only exception would be Thunderbolt 3 because the newer PCIe version is one of the main reasons why Thunderbolt 3 is faster.

    This is about the Thunderbolt side of things. Anything else is offtopic.
     
  16. g4cube macrumors 6502a

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    #17
    I defer to your superior intellect and thread management.
     

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