Mac Pro Tunderbolt bus questions

Discussion in 'Mac Pro' started by iNewbie, Jan 3, 2016.

  1. iNewbie macrumors regular

    Joined:
    Aug 25, 2006
    #1
    Hi,

    I've been running 1 Dell P2715Q 4K, 1 27inch Apple Thunderbolt monitor, 1 Dell 1680x1050 monitor and a Promise Pegasus Raid away with no problems on my 10.11.2 Mac Pro (Late 2013). I'm trying to replace the 1680x1050 with another Dell P2715Q 4K. I can't get the 3 monitors to work at the same time as the promise pegasus. Meaning if I unplug the Pegasus I can get all monitors to work but if I add the Pegasus back in it doesn't.

    I guess I'm thinking it's a thunderbolt issue. Can someone tell me the best way to plug these into the bus to I can get the three monitors and raid array working? I've tried several different ways. Currently I'm using the Mac Pro hdmi port for 1 of the 4k monitors I thought that would help but it didn't.

    Any advice would be appreciated. Thanks!
     
  2. Mago macrumors 68000

    Joined:
    Aug 16, 2011
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    Beyond the Thunderdome
    #2
    Simple, a 4k monitor @60p requires full TB2 bandwith no room for the Pegassus, you can plug this monitor to another tb port (one not-shared with other devices), organize one monitor at each TB row, the HDMI port shares it signal with the closest TB port row, so avoid this port row or only connect the pegassus there.

    TB ports are arranged on three rows (or levels as you wanna see), you can use full port bandwith at each port only if not related try this:

    row 1, port 1 connect monitor 1(video signal), row 1, port 2 connect the pegasus (pcie signal)
    row 2, port 1 or 2 connect monitor 2
    row 3, port 1 or 2 connect monitor 3
    HDMI connect monitor 3 if not connected on row 3.

    I suggest you to get an HDMI-mDP adapter and connect the Cinema TB display to the HDMI port as last resort (caring not to occupe the HDMI shared TB2 ports) if you dont connect peripherals to this tb.

    Also avoid to connect the pegasus in serie with the TB Cinema display
     
  3. AidenShaw macrumors P6

    AidenShaw

    Joined:
    Feb 8, 2003
    Location:
    The Peninsula
    #3
    I'd ask the question in a Promise community forum.

    I find it odd that the disk drive won't come up - since most of the time the Pegasus would probably use a trivial amount of bandwidth.
     
  4. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #4
    Those TB ports are far more limited than is widely publicized.

    Using an eGPU with one very quickly makes the other 5 almost useless for a high bandwidth PCIE SSD in a TB2 enclosure. The over subscribed PCIE lanes can't be switched effectively, or something.

    To use all 6 would require low bandwidth items like mice and keyboards.
     
  5. merlinmage macrumors member

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    Mar 23, 2014
    #5
    The result of a single CPU system. Good work Apple.
     
  6. rawweb macrumors 6502a

    rawweb

    Joined:
    Aug 7, 2015
    #6
    Mango, you can't connect a Apple Thunderbolt display to anything other than a Thunderbolt port and expect it to deliver video. Your statement confuses me. No adapter on the planet (that I've heard of) will do this. If it was the TD's sister, the mini display port LED Cinema Display, sure.
     
  7. Mago macrumors 68000

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    Aug 16, 2011
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    Beyond the Thunderdome
    #7
    Apple's TB Display can be connected to HDMI using an HDMI-mini DP adapter, however you loose USB/Ethernert
     
  8. rawweb macrumors 6502a

    rawweb

    Joined:
    Aug 7, 2015
    #8
    Really? That completely shocks me as the thunderbolt display won't drive video with any other adapter. I've never heard of this before.

    I kind of doubt this, but will bring an adapter to work tomorrow and try it for myself.
     
  9. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #9
    I will be amazed if this works. It would actually open the door to a hack to enable TB displays to work with cMP, something that people really want. (ie, would imply that the limit is not a functional one but a software switched one)
     
  10. rawweb macrumors 6502a

    rawweb

    Joined:
    Aug 7, 2015
    #10
    MacVidCards, I doubt it too. I've researched this quite a bit in the past and was under the understanding that the display won't drive video if it doesn't register the thunderbolt bus (I tried several things in the past before selling my display for a ACD). I've heard of people cutting holes in the display and swapping the TB cable for a mDP cable, but not this.
     
  11. Mago macrumors 68000

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    Aug 16, 2011
    Location:
    Beyond the Thunderdome
    #11
    You're right I miss that trick was my an old cinema display non-thunderbolt.

    Sorry for the "lapsus brutis".

    So my Thunderbolt port arrangement solution now considering your Thunderbolt Display, should be like this:

    Row 1,2 connect an 4k dp display on each and the Pegasus on either
    Row 3 (the one shared with hdmi) connect the Thunderbolt Display alone, this should work
     
  12. mcnallym macrumors 6502a

    Joined:
    Oct 28, 2008
    #12
    https://support.apple.com/en-gb/HT202801

    Shows how the TB Ports are arranged

    You should try plugging

    1 x 2715Q into Port 1 (Row 1) TB Bus 1
    1 x 2751Q into Port 2 ( Row 1) TB Bus 2
    1 x TB Display on Port 5 ( Row 3 ) TB Bus 3
    1 x Pegasus into Port 6 ( Row 3) TB Bus 3 alternative try the Pegasus on Port 3 or 4.
     
  13. rawweb macrumors 6502a

    rawweb

    Joined:
    Aug 7, 2015
    #13
    Excellent support article. I've got a 6,1 with 2 thunderbolt displays and all the burden is on one of the D700's according to system information (both displays listed on one card). Any idea why the load doesn't spread to the other graphics card? My fear is one GPU is basically doing all the heavy lifting (driving monitors, GUI, and computing real time video effects, etc) while the other sits there and does notta.
     
  14. mcnallym macrumors 6502a

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    Oct 28, 2008
    #14
    2009/2010 MP which also come in Dual CPU didn't come with extra PCI-E lanes available to use on the Dual CPU systems. Likely due to the desire to keep a standard board as possible.

    On the 2008 then they used the same board and simply left the second socket empty but the PCI-E came off the Chipset, so didn't make a difference with the 2009 and the move to the PCI-E on the CPU then the split the board in two. 1 board with the CPU's and 1 with the PCI-E slots on board. The CPU board being different.

    Would either have to have used 1 board and deal with these Expansion slots don't work on a Single CPU system, or have 2 boards with the extra expansion slots as well to use the extra PCI-E lanes.

    With the mini 2012 having the same socket for Quad and Dual versions then offered dual and quad. In 2014 then the CPU family uses different sockets for dual and quad so only getting Dual Core.

    Apples product history shows that they will use a single standard part rather then separate parts within a box. It doesn't follow that a Dual CPU system from Apple would be able to use the extra 40 PCI-E lanes from the extra CPU. It's possible that would, but that isn't what Apples product history would indicate.
     
  15. mcnallym macrumors 6502a

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    Oct 28, 2008
    #15
    My understanding is that it is down to the Apps being developed to be using the Second GPU. I will admit that my interest was limited to FCP X as that is my main app that use on my Mac Pro. FCP X will use the first GPU for normal Graphics Output and then the Second for the Compute/Rendering, is how I understand it. How will work with other Apps I don't know.
     
  16. rawweb macrumors 6502a

    rawweb

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    Aug 7, 2015
    #16
    Unfortunately i'm only in Final Cut these days for pet projects :(

    Most of the heavy lifting I do is done in Premiere Pro and After Effects. Feels to me like the GPU driving the displays is also the only one getting used for the general computation. Sure exporting allegedly uses the second GPU but I would love to see some more GPU action with effects like Warp Stabalization which seems to rely only on CPU while watching activity monitor.
     
  17. iNewbie thread starter macrumors regular

    Joined:
    Aug 25, 2006
    #17
    Thanks for all the information everyone. I'll try rejiggering my cables on the suggestions. Currently I think I have it (hard to tell without turning everything off and tracing)
    row 1 port 1 - Apple Thunderbolt Monitor
    row 1 port 2 - empty
    row 2 port 1 - Promise Pegasus
    row 2 port 2 - Dell 4k
    row 3 port 1 - empty
    row 3 port 2 - Dell 4k

    This actually works until I reboot. On booting up the Dell monitors don't get signal. I need to unplug the apple monitor/pegasus a bit and plug them back in and then everything starts working.

    Thanks for all the advice!!
     
  18. edanuff macrumors 6502

    Joined:
    Oct 30, 2008
    #18
    A lot of how the Thunderbolt busses work is not entirely clear, since Intel doesn't seem to have public datasheets for the TB controllers. It appears though, that DisplayPort bandwidth has no impact or bearing on TB bandwidth and the TB busses are for the most part irrelevant to DP usage, because when you plug in a DP monitor, the TB controller just switches to passing through the DP line straight from the GPU. That would account for why you have people reporting they were able to run 6 4K monitors or multiple 5K monitors off of an nMP even though that should not be possible according to TB max bus bandwidth.
     
  19. DearthnVader, Jan 15, 2016
    Last edited: Jan 15, 2016

    DearthnVader macrumors 6502

    DearthnVader

    Joined:
    Dec 17, 2015
    Location:
    Red Springs, NC
    #19
    As you say it is unclear how the PEX 8723 switch works, it seems to be buggy at best.

    By my calculations a 4k display( 3840x2160@60Hz ) should use about 1.866 GB/s of bandwidth, Apple's/Intel's Thunderbolt 2 ports have a max bandwidth of 2 GB/s.

    iNewbie, sense you have a 4k display and the Promise Pegasus on the same bus ( Row 2 ) you could download https://itunes.apple.com/us/app/blackmagic-disk-speed-test/id425264550?mt=12 blackmagic and benchmark the Pegasus drive to see if the speed gets over 134 MB/s with the 4k display connected.

    That should tell us if Displayport connected devices are passed through or share bandwidth with the Thunderbolt bus.

    EDIT:Actually it looks like you have the Apple TB Display and the Pegasus sharing the same Bus( Bus 1 )

    https://support.apple.com/en-us/HT202801

    Bus 0: HDMI Ports 5,6
    Bus 1 Ports 1,3
    Bus 2 Ports 2,4

    I don't see why, if the HDMI port didn't share bandwidth with the Thunderbolt bus, it would be listed on the Thunderbolt bus?
     

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