Can USB-C replace Thunderbolt?

Discussion in 'MacBook' started by max2015, Mar 12, 2015.

  1. max2015 macrumors newbie

    Mar 12, 2015
    Hi All,

    I'm interested in buying a Macbook, does anybody know if USB-C is able to replace thunderbolt?

    Thunderbolt has low overhead compared to USB, since it connects directly to PCI-E, however, with USB-C's alternate mode, it could be used to connect PCI-E as well.

    With max speed of 10Gbps on USB-C vs 20Gbps on Thunderbolt 2, I find it capable of attaching something like a external GPU that uses alternative mode of USB-C.

    If you see Thunderbolt 2 PCI-E enclosures, they are usually a few hundred bucks, and one reason why it's expensive is that Thunderbolt 2 requires licensing fee from Intel. But not USB-C. Hence in the future, can we find PCI-E enclosures for USB-C?
  2. redheeler macrumors 604


    Oct 17, 2014
    The USB Type-C port on the rMB only supports speeds up to 5 Gbps (as stated on Apple's website), not 10 Gbps. Compare that to Thunderbolt 2 (20 Gbps) and the upcoming Thunderbolt 3 (40 Gbps).

    I'm sure we'll see some USB Type-C enclosures, but it is still no substitute for Thunderbolt.
  3. ParanoidDroid macrumors 6502


    Sep 15, 2013
    Venusville, Mars
    Does anyone know how the TB3 connector will look like? It can only have a future if it meets Jonny Ive's obsession with thinnes.
  4. Meister Suspended


    Oct 10, 2013
  5. flyinmac macrumors 68040


    Sep 2, 2006
    United States
    Thunderbolts passing has been indicated. FireWire was great in its day also, but killed off before its time. History repeats itself. USB-c is where Apple will move.

    We'll see thunderbolt being phased out similar to FireWire over time.
  6. redheeler macrumors 604


    Oct 17, 2014
    Like it does now but a little thinner, so it should be safe. 3 mm to be exact.
  7. bkkcanuck macrumors regular

    Mar 17, 2015
    5Gbps / 10Gbps / 20 Gbps

    You are correct, the current Macbook supports USB 3.1 Rev 1 Type C connector. USB 3.1 rev 1 in this case is actually USB 3.0, they renamed it for "consistency" but ended up totally confusing the situation. (5 Gbps)

    Once chipsets are deployed that changes to support the actual USB 3.1 standard the equivalent would be USB 3.1 Rev 2 Type C connector which will support 10 Gbps.

    I have read that the C connector itself supports up to 20Gbps (future), and I have read the new macbook supports Displayport 1.2 natively -- which has a much higher bandwidth than 5Gbps which makes me think that yes, the current USB data stream is limited to 5Gbps but when you connect up the displayport it may support higher speeds than the USB data stream.

    It also gets me wondering whether the reference to 20Gbps is a reference that another alternate mode that Apple will add in the future will support thunderbolt 2 data streams..... I am not technical enough to know if that is possible.

    Of course thunderbolt 3 comes out in a few months with the Skylake chipset and the maximum speeds for that are 40Gbps. I would think that the Mac Pro will continue supporting the top speeds possible, while maybe the macbook pro line might cap out at 20Gbps.

    The situation right now is cloudy for me, but by the fall we should begin to have a clearer picture.
  8. slenpree, Mar 17, 2015
    Last edited: Mar 17, 2015

    slenpree macrumors 6502a


    Apr 13, 2010
    Thunderbolt replaces (or is an alternative to) internal PCIe expansion

    Thunderbolt 1 - DP1.1(3k) - PCI Express 1 Bus
    Thunderbolt 2 - DP1.2(4k) - PCI Express 2 Bus
    Thunderbolt 3 - DP1.3(5k) - PCI Express 3 Bus

    Good for fast/large storage arrays, especially solid-state. Video-desks, audio interfaces/sound cards, external graphics cards or video rendering processors, high resolution desktop displays at 60Hz, 10Gbit fibre Ethernet adapters, etherchannel adapters, capture cards from blackmagic and so forth. You get the idea - high bandwidth / specialist.

    USB on the other hand has, and always will, be for consumer (or basic) peripherals

    Good for portable bus-powered mechanical drives, Small bus-powered SSD drives, Memory sticks, HDMI mode for connecting to TV, DVD writer, Mice and Keyboards, Gigabit Copper Ethernet adapters, Webcams and so forth. You get the idea - lower bandwidth / common connectivity.


    Apple did the right thing by configuring the non-pro MacBook with USB only, because that's all non-pro people need. However I expect all MacBook Pro's (and MacPro's) going forward will continue to use USB and Thunderbolt, probably USB with the type-c connector in future for convenience. If they do converge in future, then expect this to be a few more years away.
  9. bkkcanuck macrumors regular

    Mar 17, 2015
    Not being an engineer, I could be wrong but I actually believe a USB-C connector could support thunderbolt as an alternate data stream (as opposed to the USB standards themselves).

    USB-C supports USB Power charging of 100 watts.
    Thunderbolt 3 - same 100 watts.

    USB-C seems to have 4 data high-speed data lanes for alternate data streams (currently used for displayport and HDMI devices)
    Thunderbolt supports 4 high-speed data lanes (most of the pinouts are grounds).

    So the rumours of Apple having at least some input in the USB-C standard could mean they have managed to be able to support both the USB standards, displayport standard, hdmi standards and hopefully thunderbolt standards.

    The lack of thunderbolt in the macbook could just be a compromise because of power and PCB board space for supporting chipsets.

    The alternate data streams are native.... displayport datastreams are displayport datastreams just a different connector type.

    So if my theory is correct, going forward Apple could build in USB-C connector ports (multiple) which you can plug in slower / higher latency USB devices, or you could plug-in display-port monitor, OR you could plug-in an existing thunderbolt device. In other words -- the only thing that changes is that the port type itself not the devices.
  10. slenpree macrumors 6502a


    Apr 13, 2010
    First, i'd like to see USB-C replace the lightning cable! not that there is anything wrong with lightning just that they are almost identical in usage (USB connection in either direction, with power in either direction and a HDMI mode).
  11. bkkcanuck macrumors regular

    Mar 17, 2015
    I think USB-C will replace the lightning cable and the magsafe adapters. I suspect part of the reasons for moving towards a common standard is pending legislation in Europe which is eventually going to mandate a common standard for charging on all electronic devices that transmit or receive wireless (this includes all phones, iPad, and potentially anything they deem to add to that list). It makes sense to jump ahead and define a standard that works for you rather than wait for the European Commission to define it for you. This way they don't end up with having to manufacture a special phone/ipad for europe.
  12. leman macrumors G3

    Oct 14, 2008
    I am fairly sure that Thunderbolt is here to stay. It is a high-performance, super-flexible connection for (semi-)professional applications. In a high-performance segment, especially when low-latency PCI-e functionality is required, USB-C is not even remotely close to being competitor for Thunderbolt.

    USB-C makes a lot of sense as an all-purpose consumer port. But Thunderbolt should remain as a specialised high-performance professional port (at a higher price point). There is place in the market for both interfaces.
  13. bkkcanuck, Mar 17, 2015
    Last edited: Mar 17, 2015

    bkkcanuck macrumors regular

    Mar 17, 2015
    I think you are missing the point, and the difference of the technology.

    USB 3.0 (which is now called USB 3.1 revision 1 - is a 5Gbps datastream).
    USB 3.1 (which is now called USB 3.1 revision 2 - is a 10Gbps datastream).

    USB-C is just the connector type. I believe it has 24 pins.

    Certain pins are reserved for USB 2, certain pins are reserved for USB 3.x, AND THEN certain pins are reserved for "alternate data stream". I believe there are 4 pairs for high-speed data lanes.

    As it stands now, USB carries multiple different data streams with their own standards. So it can carry USB data AND displayport on the same connector (where as you would have two connectors before). The display data does is not encapsulated in USB data it is just as it was before.

    What this means is you can have a cable that is a USB-C to Displayport cable and connect up and existing displayport monitor.


    You could connect up an existing thunderbolt device using a Thunderbolt cable -> USB-C connector. It would have EXACTLY the same performance as if you had plugged into one of the older thunderbolt ports....


    You could connect up an existing USB device and an existing Thunderbolt device using a USB/Thunderbolt dongle.

    Assuming my theory is correct (and there is enough data lanes) you could have 3 (or more if the chipsets support it) USB-C ports on the side of a laptop and plug in any combination of USB / Thunderbolt / Displayport / HDMI / or charger devices.....

    Which is to me is WAY more exciting than what has been announced so far since it would be both very flexible and very powerful.
  14. leman macrumors G3

    Oct 14, 2008
    What you write makes sense. Would be interesting to see if this will be possible.
  15. Steve USB macrumors newbie

    Mar 17, 2015

    The chipsets were initiated in USB3.1, and are just becoming available. They changed the coding to increase data thru put, Gen 1 is 4Gt (gigatransfers - actual data), Gen 2 is very near 10Gt.

    I can confirm USB Type C is designed for 10GHz, suitable for a binary code of 20Gb.

    20Gb was a spec goal from the start, Apple didn't join the committee until 7 month in.

    HDMI is not an Alternate Mode for USB Type C. DP has to be converted the HDMI in the adapter cable.

    The 4 lanes allow for Alternated Modes, but it could just as well be two 10Gb USB channels.

    Alternate Modes were part of the spec goals before Apple join the USB Type C committee.

    USB Power Delivery Gen 1 was released in 2012, with the same voltages and currents. It was implemented much better in the Type C connector.

    Correct in both cases

    4 pins are used for USB2, to make it flappable.

    One pin, the CC, identifies a connection has been made and is the communication line to negotiate power.

    One pin provide power to any electronics in the cable.

    2 pins are reserved for "future use", and are used in DP over Type C.

    Only one problem, Thunderbolt has not applied to become an Alternate Mode (to date only Display Port and MHL)

    My expected implementation will be:

    Monitor with 2+ USB Type C receptacles, along with several USB Standard A, LAN, etc.

    Plug in your keyboard & mouse to the monitor
    Plug in you high speed hard drive to the monitor
    Plug your gigabit LAN into the monitor.

    Plug your laptop into the monitor using the Type C cable, and:

    1. The monitor provides power to the laptop
    2. The laptop provide video to the monitor over DP
    3. One USB 3.1 Gen 2 port connects to the monitor as hub, where the USB3.1 Gen2 accesses LAN and the hard drive, the USB 2.0 access the keyboard and mouse.

    One connector docking.
  16. newellj macrumors 603

    Oct 15, 2014
    Boston, MA, US
    But for clarity, the rMB is only going to do data transfers at ~5 gbps, according to the Apple specs.
  17. bkkcanuck macrumors regular

    Mar 17, 2015
    Unless you have read different specs than I have, your clarity is not what the technical specs say (below copied), it states that USB 3.1 Gen 1 data up to 5 Gbps - not data in general:

    USB-C port with support for:
    - Charging
    - USB 3.1 Gen 1 (up to 5 Gbps)
    - Native DisplayPort 1.2 video output
    - VGA output using USB-C VGA Multiport Adapter (sold separately)
    - HDMI video output using USB-C Digital AV Multiport Adapter (sold separately)
  18. bkkcanuck macrumors regular

    Mar 17, 2015
    Thanks Steve for the detailed and apparently knowledgable response. Two questions if you know the process:

    - How long does it reserve an "Alternative Mode"?
    - Can Apple do it themselves, or do they require Intel to apply?
  19. dusk007 macrumors 68040


    Dec 5, 2009
    If one just looks at the mini Displayport that Thunderbolt has adopted the connects are like 4 pairs for the data. If you use the ones on both sides of the type-c there is actually plenty to just make Thunderbolt adopt this new port and drop the mini displayport.

    All they need is put a thunderbolt chip behind it and well Apple can make it happen if they want to. Technically it is possible and would be the ideal solution. It would only be confusing for some people who will then not understand why there is this one port but it requires specific cables for this or that use or notebooks having the same port but only supporting different protocols. Could get confusing but it is bound to be anyway, with this one only supporting USB 3.0 and current DP, while future type-c will support faster DP, USB 3.1 and possibly Thunderbolt.

    I think this time they wanted a simple logic board and only went with what the chipset support, hence USB 3.0 only. A Thunderbolt chip not only costs it would need quite a lot of space on the logicboard, so would have a extra USB 3.1 controller. I could see Apple going for Type-c only and supporting everything over that one single port though the MBPs will probably bring more than one of those.
  20. maflynn Moderator


    Staff Member

    May 3, 2009
    No, you cannot replace it.

    Plus I think outside of Apple, Thunderbolt is dead, where as USB-C is being embraced by more makers.
  21. Steve USB macrumors newbie

    Mar 17, 2015
    Should be knowledgeable, I was on the committee, that said, I can disclose public domain information (and dispel inaccuracies).

    Not sure what you are asking about Alternate Modes.

    DP was identified early as an Alternate mode (many of the participants are on both committees). HDMI requires all 4 high speed pairs, DP can do 2 or 4 (2 pairs leaves room for one USB3.1).

    The way an Alternate Mode is added is the committed that controls the standard (VESA controls DP) asks the USB-IF. I'm not sure of the approval process.

    Apple has a lot of horse power, but it can't commit for VESA, because there are many other companies on that committee, enough combined can veto Apple.

    Apple did join the USB Type C committee until after DP was identified and a desired Alternate Mode, so they just added their vote.

    Is that answering your questions?
  22. bkkcanuck macrumors regular

    Mar 17, 2015
    Thanks, I think so.... short answer is that Intel -- not Apple would have to start the process for adding Thunderbolt. And you are not sure of how long it takes - though personally I suspect that if Intel was behind the push it probably would not take long, since there is not as much USB interoperability at stake with it.
  23. Theophil1971 macrumors 6502


    Mar 20, 2015
    I'm thinking that Apple probably intends USB-C to be the standard for their entry level laptops (rMB, which will eventually replace the MBA line). Rev 2 (10gps) of USB-C will be hailed as a feature on future upgrades of the rMB line. Thunderbolt 2, 3, etc... will continue to be featured on the rMBP line, for power users who need the higher spec. But the rMB will not utilize it, and users will have to choose between the two different laptop lines depending on their use needs.
    Just a guess...
  24. Paulsukhu macrumors newbie

    Oct 29, 2012
    I think Thunderbolt will be around as long as it is supported by Apple and Intel.

    I expect to see TB 3 only in desktops and higher end laptops, especially when 4K and 5K monitors are priced within reach of "prosumers". The same types of devices that currently have Thunderbolt and/or DisplayPort interfaces.
  25. Steve USB macrumors newbie

    Mar 17, 2015
    I have not heard anyone talking about Thunderbolt over USB Type C. That is a group at Intel I haven't talked with since Light Peak.

    There is a significant difference in cost in the cables for USB Type C and Thunderbolt, being Thunderbolt has a lot of active circuitry, USB Type C only an IC that identifies the cable (being a new technology, we wanted to allow for 10+ years of evolution, passive markers didn't offer enough options).

    One concern, as more Alternate Modes are added, there are more combinations that won't work together. With DP specified, MHL approved, adding Thunderbolt would add a third video protocol. Lets say I have 3 laptops (DP, MHL & TB), and 3 displays (DP, MHL, & TB), either I have 9 combinations, where only 3 will work, or I have a very complicated chipset that works with all 3 protocols - counter to cost reduction.


    I search the Intel website for Thunderbolt 2, and get results, Thunderbolt 3, nothing.

    When I search Google, most of the news about Thunderbolt 3 was April 2014, with one in November 2014.

    I would wonder why Apple is adopting a protocol that directly competes with Thunderbolt? Why not spend the same effort and push Thunderbolt 3 into release?

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