nMP Thunderbolt Bus Question

Discussion in 'Digital Video' started by mBox, Sep 25, 2014.

  1. mBox macrumors 68020

    Jun 26, 2002
    Posted this on Mac Pro section:

    Does anyone know how to do the math as far as bus consumption with the new Mac Pros?
    I have two Apple Cinema 30s, two Sonnet Echo Express III Rack with RED ROCKET in one and Pro Tools HDX PCI on the other, a G-Tech StudioRAID 8TB and a Black Magic Design UltraStudio 4K Video Converter.

    Ive tried numerous bus configs but it seems like the roll of a dice at times when running config with software such as Avid Media Composer, Pro Tools and Resolve.

    It fails at different levels and dont want to explain but if anyone can direct me to where one can find out of were sucking the life out of this thing.
  2. deconstruct60 macrumors 604

    Mar 10, 2009
    There are three Thunderbolt controllers int the Mac Pro 2013. In Apple's terminology they provision three Thunderbolt buses which are outlined here:


    In particular is the note there:

    "... Note: Attach displays to different Thunderbolt busses when possible (see figure below). .. "

    Each port on the Mac Pro can either be a Thunderbolt (TB) or mini DisplayPort (DP) port depending upon what is immediately plugged into it. (and possibly what is plugged into the HDMI for bus 0. Each bus only can support at most two displays. )

    Given the number of TB devices to follow there isn't a good reason to put two of these displays onto the same TB bus. Similarly, unless some distance requirement, little good reason to not to directly connect these.

    Directly connected this is DP bandwidth not TB bandwidth. You 'loose' an operational TB port, but you don't loose any TB bandwidth. Given have 6 TB ports ( 4 left ) it is a decent trade off to manage bandwidth.

    Both of these tend to push data in one direction. TB is bidirectional so there is inboud and outbound ( relative from Mac Pro) bandwidth. Two major inbound devices on the same TB bus are going to compete with one another.

    Devices that both read (inbound) and write (outbound) alot of data may need isolation. Similarly, devices that aren't concurrently used very often will share a bus direction better.

    rather course grain you can use Activity Monitor to see disk activity. ( iostat is a command line tool to probe system storage activity ). If trying to probe low level PCI-e activity that TB encapsulates and transports it is more complicated ( Instruments). This page has a set of tools.


    But first step would be looking into the TB devices support docs to see what they outline as being the bandwidth requirements/specs for representative loads.
  3. mBox thread starter macrumors 68020

    Jun 26, 2002
  4. mBox thread starter macrumors 68020

    Jun 26, 2002
    Thanks again deconstruct60 for the tips.

    So far I havent had issues with the following Thunderbolt config:

    Thunderbolt Bus 1
    Port 1 - Apple Cinema 30"

    Thunderbolt Bus 2
    Port 2 - Black Magic Design UltraStudio 4K

    Thunderbolt Bus 0
    Port 5 - Apple Cinema 30"
    Port 6 - GRAID STUDIO 8TB

    Where the issues start is when Pro Tools start to hiccup switching back and forth with Avid Media Composer.
    Not once did I see an issue with the RED ROCKET which is usually the first culprit in these kind of setups.
    The card is someone useless due the shear speed of the new Mac Pro but there are days when I want to see 4K/5K clips at FULL DEBAYER plus it does help speed up transcoding from R3D to <insert format here> :)

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