Thunderbolt expectations

Discussion in 'MacBook Pro' started by grizzelda73, May 8, 2018.

  1. grizzelda73 macrumors newbie

    Feb 26, 2018
    If I am to benefit from the speed of the 2 Thunderbolt (USB-C) sockets on my mbpro, do the connected devices need to be specifically Thunderbolt capable also? And if not will the data transfer speed be only as fast as the slowest device? If anyone could enlighten me I'll at least know which peripherals not to buy. Thank you.

    p.s. It's a basic 2017, 13" 128gb model.
  2. chabig, May 8, 2018
    Last edited: May 8, 2018

    chabig macrumors 603

    Sep 6, 2002
    If you want Thunderbolt speed, you need Thunderbolt devices. That USB-C ports also support ethernet, Firewire, USB, DisplayPort, HDMI, VGA, and some protocols that I missed. The connection speed between any two devices depends on the speed of the data transfer protocol. USB devices get USB speed, Thunderbolt devices get Thunderbolt speed, and so on. And yes, when any two devices communicate, speed is limited by the slowest device.

    By the way, Thunderbolt is overkill for a single hard drive, as the drive itself will be the limiting factor.
  3. Samuelsan2001 macrumors 604

    Oct 24, 2013
    Your machine has thunderbolt 3 not 2, to get those speeds you need thunderbolt 3 peripherals connected with a thunderbolt 3 cable, that can take advantage of the bandwidth, things like 5k screens, eGPU enclosures and TB3 raid systems will make use of this to be honest for most other uses usb c is just fine.
  4. mmomega, May 8, 2018
    Last edited: May 8, 2018

    mmomega macrumors demi-god


    Dec 30, 2009
    DFW, TX
    Sometimes it goes deeper than just looking for "Thunderbolt capable"
    Thunderbolt just means that that external device has the ability to send and receive data over that particular cable.
    The speeds at which it is capable of and actually doing can be on opposite ends of the spectrum.

    If you have a Thunderbolt 1, 2, or 3 external hard drive. You will only get speed based off of the slowest link in the chain. If it is a platter based hard drive you are looking at 120 MegaBytes per second maximum, even if it is in a Thunderbolt 3 enclosure.
    If it is a SATA 3 based Solid state drive. Now you are at 550 MegaBytes per second maximum. (give or take a few MBps)

    So even if Thunderbolt 3 is capable of 5 GigaBytes per second, you will not ever see that speed unless you have actual hardware capable of even transmitting and receiving at that speed.

    Also. Say you have a computer with an internal hard drive. Platter. So it will read and write at approximately 120MegaBytes per second. If that computer has Thunderbolt 1 or 2, let's say a Thunderbolt 2 external SSD, so maximum read and write is 550'ish MegaBytes per second. If you are sending or receiving data to or from the internal platter drive to the SSD, you are limited to the speed of the slowest link, which is now the internal hard drive so even though you have an 500+ MegaBytes per second capable device, if it has to send or receive from that platter drive everything slows down to 120 MegaBytes per second.

    Another example.
    I had purchased an external RAID capable Thunderbolt 1 enclosure several years ago. Thunderbolt 1 is capable of 1.25 Gigabytes per second read and write.
    That drive only sent and received at 120 MegaBytes per second with RAID 0 Solid State drives.
    Because that enclosure only had a SATA 1 controller built in, I was then limited to SATA 1 speeds on SSD's RAID'd in a Thunderbolt enclosure.

    The whole thing can be quite confusing up front to consumers until you put in the time to learn where the limitations are in the system.

    And then USB-C is it's own other thing.
    USB-C is just a shape of the plug connector essentially.
    Like Thunderbolt it is capable of very high speeds but can be limited down based off the the hardware connected.
    Example with this that I've had experience with, not all USB-C cables are created equal. I have a handful that only transmit at USB 2.0 speeds, some that do USB 3.0 speeds and a couple that do USB 3.1 speeds.
  5. grizzelda73 thread starter macrumors newbie

    Feb 26, 2018
    A late thank you for all your help overwhelmed with advice future-proofed...for now at least!
    --- Post Merged, May 14, 2018 ---
    Thanks for the help.
    --- Post Merged, May 14, 2018 ---
    That's an incredibly informative reply, I am still digesting it and sorry for the delayed reply.
  6. mmomega macrumors demi-god


    Dec 30, 2009
    DFW, TX
    No problem, I've just been going through things like this with Thunderbolt since v1 in 2011 I believe. It's been a little while.
    I'd rather pass on any information I have, sometimes it may be too much, but at least someone has it and can hopefully make a better decision for them moving forward.
  7. Fishrrman macrumors P6


    Feb 20, 2009
    Thread title:
    "Thunderbolt expectations..."

    "Expectations" -- high

    Delivery -- low.

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