Thunderbolt 3 and MacBook Pro Late 2016

Discussion in 'MacBook Pro' started by palyons, Nov 15, 2016.

  1. palyons macrumors member

    Mar 2, 2010
    So, a few hours ago I received my MacBook Pro Late 2016 15" with Touch Bar and have a curious question about the Thunderbolt speeds. While it says on the Apple site it's 3, I have to wonder, is it really? Thunderbolt 3 clearly states up to 40 Gb/s. While this on the other hand states it's 20 Gb/s the speed of Thunderbolt 2.

    Attached Files:

  2. johngwheeler macrumors 6502

    Dec 30, 2010
    I come from a land down-under...
    Well spotted, and an interesting question!

    As we know, the TB MBP 13 has reduced-bandwidth ports on the right hand side due to the CPU limitations, but the 15" should not suffer from this.

    Is the 40Gbps in both directions or 20Gbps in each direction, totalling 40Gbps? Hopefully not!

  3. curmudgeonette macrumors 6502

    Jan 28, 2016
    Notice the x1 in the screen shot? TB3 has two 20Gb/s outbound lanes and two 20Gb/s inbound lanes. Thus there's 40GB/s bandwidth in each direction.
  4. johngwheeler macrumors 6502

    Dec 30, 2010
    I come from a land down-under...
    Yes, but does "port" equate to the physical TB3 ports? So instead of having 2 x 40Gbps TB3 ports, the TB3 bandwidth is spread across the two ports for each TB3 bus, i.e. 20Gbps each? How many TB buses are there - I assume the 15" MBP has 2 TB controllers and the non-touch MBP 13 only one.

    What is the total bandwidth the 15"? Is it 4 x 40Gbps or 4 x 20Gbps?
  5. johngwheeler, Nov 15, 2016
    Last edited: Nov 16, 2016

    johngwheeler macrumors 6502

    Dec 30, 2010
    I come from a land down-under...
    Adding to this thread, I found the following:

    It is fairly detailed, but two paragraphs stood out:

    "The dual-port SKU supports two Thunderbolt 3 connectors. It takes four lanes of PCI Express Gen 3 as an input and two full (four-lane) links of DisplayPort 1.2a. "

    -> which implies that the dual port controller can handle 4 x 8Gbps + 2 x (4 * 5.4Gbps), which with the protocol overhead removed equates to c. 80Gbps, so maybe it is 40Gbps per connector.

    "Because a Thunderbolt 3 chip can support either one or two connectors, there is the need to provide more capability than can be used on a single connector. Many Thunderbolt 3 usages are around single-connector consolidation, but there are also many consumers who want huge expansion with di erent devices on each port. "

    --> which also may imply that a single connector may get less bandwidth the combined capacity of the controller (obviously!)

    The diagram in figure 4. is also interesting, and might explain the OPs view from the System Report. The physical connector seems to actually have two bi-directional data streams of 20Gbps, so a combined logical bi-directional stream of 40Gbps (i.e. in each direction).

    *But*, the MBP 15 would presumably have four of these "port pairs", and the OP is only showing one. Is this correct?

    [Edit: apparently the reported bus speed, e.g. 20Gbps, can vary according to the connected devices. If a TB2 device is connected, it may only report "up to 20Gbps" even if the port will support 40Gbps, as only a one of the two 20Gbps bi-directional channels is used (per port). Plugging in a TB3 device may change the reported bus speed]
  6. joevt macrumors 6502

    Jun 21, 2012
    You don't have any devices connected. Maybe the numbers will change when you do. I don't know what the Link Status bits mean. They may be documented in an Intel manual that they do not make available publicly, unlike for their CPU's, or I can't find it.

    I've attached a screen shot of my MacBook Pro 2015 with the following connections:
    - OWC Thunderbolt 2 Dock
    - Apple Thunderbolt 3 to Thunderbolt 2 Adapter
    - AKiTiO Thunder3 Duo Pro
    - StarTech Thunderbolt 3 to Dual DisplayPort Adapter - 4K 60 Hz - Windows only

    The last two are Thunderbolt 3 devices and say 40 Gb/s. I had to use the "TB3-enabler" patch to get the Thunderbolt 3 devices to be usable by macOS, otherwise it would just say "Unsupported" in that screen shot.

    Attached Files:

  7. dyn macrumors 68030

    Aug 8, 2009
    There simply are different cables for Thunderbolt 3. The cheaper ones will only do 20Gb/s (these were specifically created to make things cheaper).
  8. Mindinversion macrumors 6502


    Oct 9, 2008
    This is a VERY important thing to note regarding speeds. To get 40 Gb/s you need an ACTIVE Thunderbolt 3 cable. They're just becoming available in sizes larger than .5 [which is what the Razer Core ships with] and carry a price premium over passive cables. It gets even more convoluted since there are active 40 GB/s, 20Gb/s, and then USB Type C cables gen 1 and 2 that are 5 GB/s [think "new MacBook"] and 10GB/s respectively.

    For the record, the cable that ships with the 2016 MacBook Pro line is *NOT* an 40Gb/s active TB3 cable.
  9. danniexi macrumors 6502

    Jan 7, 2012
    Hell, the included USB-C "charge" cable is not even USB 3.0. It can only transfer speeds of up to USB 2.0 spec (480Mbps).

Share This Page

8 November 15, 2016