Laptops without bandwidth sharing of Thunderbolt 3/USB-C ports

Discussion in 'Buying Tips and Advice' started by hajime, May 26, 2018.

  1. hajime macrumors 601

    Jul 23, 2007
    Hello, I am considering to buy a TS3+ Thunderbolt 3 dock. I plan to use it to drive an external 4K display at 60Hz (via a HDMI 2.0 port at the back of the 4K TV), usb devices and a high speed SSD. In a few months, I may add an eGPU.

    It has been to my attention that although some Windows laptops have multiple Thunderbolt 3 / USB-C ports, they share bandwidth. Using one will lower the bandwidth of the others. This is certainly a turn off. Do MBP 2017 (and up-coming 2018) 13" and 15" models have such limitation?
  2. Samuelsan2001 macrumors 604

    Oct 24, 2013
    The 13 inch has two slower and two full speed the 15 inch are all full speed.
  3. hajime thread starter macrumors 601

    Jul 23, 2007
    Thanks for the info. How to find this out by myself when the new 2018 models come out?
  4. killawat macrumors 65816

    Sep 11, 2014
    It's unlikely to change based on how Apple allocated the bandwidth to each of the ports. I don't think there will be any extra PCIe lanes available to allocated to additional thunderbolt bridges, but again that depends on what package they choose from Intel.

    Apple may put this in the marketing material for the new MBP, but if not you'll need to wait for an ifixit teardown or readout of the system information report to see if the number of thunderbolt controllers increased (for the 15") or if Apple allocated full bandwidth to the 13" ports.

    By the way having dealt with eGPU before, you should be fine regarding bandwidth on any of the systems. I don't think you'll bottleneck the TS3+ with only a single 4k display. Multiple 4k displays are where things get dicey. Naturally the conversation changes with a 5k display. And keep in mind, once you build your eGPU, you lower your bandwidth requirements for your TS3+ because you won't need to drive 4k off of it.
  5. mroy16 macrumors regular

    May 28, 2017
    To be clear, the current 15" MBPs have 4x PCIe 3.0 lanes shared between the left ports, and 4x lanes shared between the right ports. Apple doesn't really document this anywhere, and I'd be surprised if any other manufacturers are reporting more clearly. If you are really concerned about saturating the TB3 bandwidth, you'll need to find teardowns that identify the PCIe lanes and TB3 controllers.
  6. hajime thread starter macrumors 601

    Jul 23, 2007
    Here is what I am considering to do:

    Since I don't like dongles hanging near the thin MBP to make it ugly, I will buy a Caldigit TS3 Plus so that one thin line goes out of the MBP to the dock. I plan to connect some usb devices to the dock. For example, thumb drive, external drive (not sure that interface yet), Logitech Unifier usb dongle for the mouse and a usb cable to change the keyboard. I plan to add a Displayport to HDMI adapter and a HDMI 2.0 cable to connect the 4K TV to the TS3 Plus. In a few months or weeks, I may add a eGPU to do CUDA computations. First question is without eGPU, is the MBP 2017/2018 capable of 3D CAD model manipulations and 3D gaming at 4K under Bootcamp Windows 10? Second question is can I use this hardware setup and Ubuntu Linux to drive a 4K display @ 60Hz for CAD and productivity tasks. Meanwhile, not connect the eGPU to drive the 4K display but to dedicate it to do CUDA computation under Ubuntu Linux.

    Do you see any possible issues with bottle-necking the Thunderbolt 3 bandwidth in these cases? Is it better to get the 15 inches model just in case?

    As far as I know, the Carbon X1 6th gen 2018 model has two thunderbolt 3 ports but they share bandwidth. Do you know if I will encounter bottleneck in bandwidth issue if I use it instead of the MBP 2018?
  7. Samuelsan2001 macrumors 604

    Oct 24, 2013

    Well it won't do 4K gaming no slim light laptop will do that well, its that simple, even an imac will struggle with that let alone a thin light laptop with a mediocre dGPU (15 inch only of course if this is your use case the 13 is just not powerful enough for you). Even a 1080 equipped water cooled PC can struggle with 4K gaming on AAA games.

    It will run 3d CAD computations pretty well I'm sure, pro apps tend to run fairly well on a MacBook pro.

    I am unsure why you want a laptop for this use case, a 5k imac or even the imac pro seems a much more sensible option for you, with a small laptop for on the go and all the computational power you need at home.
  8. mroy16 macrumors regular

    May 28, 2017
    You should be able to find the bandwidth for each device you intend to connect. Simple things like a mouse and keyboard don't really matter, but you can look at the bandwidth requirement for running displays at various resolutions and refresh rates.

    If everything, including the eGPU, comes close to or exceeds 40 Gbps, I would recommend the 15" model, as it has 2 4-lane controllers. Though as @Samuelsan2001 points out above, it sounds like other devices may fit your use case better.
  9. hajime thread starter macrumors 601

    Jul 23, 2007
    I need portability. While on the go, I don't need high-end GPU power.
  10. Samuelsan2001 macrumors 604

    Oct 24, 2013
    You want to do 4K gaming and 3D cad the only thing you need is high end gpu power, you are also talking about connecting external screens thunderbolt docks etc this sounds exactly like a case for a desktop not a portable all rounder.
  11. hajime thread starter macrumors 601

    Jul 23, 2007
    I may also want to connect an IPP as a tablet.
  12. killawat, Jun 1, 2018
    Last edited: Jun 1, 2018

    killawat macrumors 65816

    Sep 11, 2014
    Ok pretty straight forward requirements. First you will definitely see some performance loss if you plug in your eGPU into the dock, even with nothing else hanging off the dock. On CUDA, For all intents and purposes, AMD is plug and play on MacOS, and Nvidia is plug and play in Bootcamp. I have no idea about linux compatibility, but from what I can remember, today you can drive eGPU in linux but it requires a fair amount of hacking; this is from a cursory glance on the forums. You really should "consult" them on the matter because they have the most experience.

    Nvidia and MacOS don't really play nicely, everything that is available today is through various hacks. Yeah the drivers are there but they were never meant to encompass eGPU use. The community is working round the clock to maintain compatibility, but it's always a crapshoot on the next release without unofficial support.

    AMD and Bootcamp don't play nicely because of Radeon cards requiring a greater amount of bandwidth. I'm not sure if the 13" MBP is impacted by this, but the 15" definitely is.

    The solution that would require the least amount of hacking would be to use the internal GPU for MacOS and linux related tasks and have an nvidia eGPU for bootcamp, again this is virtually plug and play. eGPU AMD/MacOS is fantastic, but in cruel fate you may have issues with Bootcamp. Yes you can get AMD cards to work in Bootcamp but on my 15" it was an uphill battle that I ultimately gave up on.
  13. hajime thread starter macrumors 601

    Jul 23, 2007

    Thanks. Actually one of the main reasons I look for eGPU is that I want to use Nvidia GPU that Apple no longer offers for the MBP line. Another reason is to avoid getting Windows laptop with heat/crazy fan issue.

    I don't need to do GPU intensive stuffs under Mac OS so I can live with whatever comes with it. For Linux, I certainly want to make Nvidia-eGPU works as I need to do CUDA computations under Linux for my job. For Windows, it would just be nice if I could do some high-end 4K gaming. Not an absolute requirement though.

    I shall check with forums.
  14. ThunderSkunk, Jun 1, 2018
    Last edited: Jun 1, 2018

    ThunderSkunk macrumors 68030


    Dec 31, 2007
    Milwaukee Area
    We have a lot of designers that appear have the same requirements as you. One machine, with all their settings and customizations tailored to their process, that stays with them. When at a desktop, can plug in to a dock w/eGPU & large pro display to become a decent workstation, but when it's time to hit the road, grab it and go, and you have everything with you exactly as you are used to using it. If people understood how much time Cadmonkeys spend customizing CAD for their personal preferences and project workflows on a regular basis, they'd realize how impractical and frought having a desktop and a separate workstation for each user is. One machine, capable of both being portable or even mobile when on the road, & decent as a desktop when at a desk, is the ideal.

    As for tablets though, we've found using iPad Pros as shared displays via duet etc prohibitively problematic. If you use any kind of pointing device with absolute coordinates, they never extend on to the iPad, so your cursor never reaches it. Also they tend to screw up your display arrangement in the coordinates config every time they're unplugged, switching display 1 to 2, which you then can't access... nothing but headaches. We use Wacom Cintiq Pros for the tablet interfaces instead of iPads. It's a proper display, with 16" of real estate, much better digitizer, more accurate, & a lighter, passive stylus is better to work with & you never have to worry about charging.

    Luckily, solidworks & inventor will run quite well on just about any of these machines i5 or above. I was amazed at how well inventor RT rendered complex models on a 2013 i5 MacBook Air w only 8gb of ram & a wacom intuos hooked up. Maybe the most comfortable modeling experience ever. Gaming I don't know about, probably not, but computers seem to have become far more powerful than CAD actually requires at this point. I mean I can spin models around on a 2009 MBP 17, with a core2duo chipset without issue.
  15. vkd macrumors 6502a


    Sep 10, 2012
    There's a lot of new information there for me, and I thought I kept up to date!

    I understood that although Apple are more aligned with AMD GPUs as of late, they have used nVidia in the recent past and drivers are included in macOS, for up-to-date drivers nVidia themselves are providing web-downloadable drivers for their GPUs for use in Apple systems.

    Final point, and I know I am well out of date on this one, but upon installing Bootcamp on my mid-2011 iMac equipped with an AMD Radeon 6770M GPU, I installed the Apple Bootcamp drivers in the Windows installation and it works just fine. Not a problem.

    All of this seems to contradict what you are saying though, so I have my doubts about my information, please take it with a pinch of salt, I may be completely wrong.
  16. killawat macrumors 65816

    Sep 11, 2014
    My post above is focused on eGPU . AMD and nVidia GPUs in iMacs and MacBook Pro continue to be supported in macOS and bootcamp.

    Off the shelf , newer nVidia PCIe graphics cards have a varying degree of compatibility depending on if the graphics card is EFI flashed.

    nVidia eGPU in macOS is 100% unsupported by Apple. Some connectivity options are available primarily through community driven efforts.
  17. shaunp macrumors 68000

    Nov 5, 2010
    the latest XPS 15 doesn't have bandwidth sharing. and it has a 6-core i9. Take a look
    --- Post Merged, Jun 4, 2018 ---
    The more I read of your requirements the more I think you should get an XPS15. Dell have good Linux support on this model. It also has a GTX 1050. Not quite good enough for 4K gaming, but you don't need to go that high on a 15" screen. Drop it down a peg and it's more than enough - I had the older version with the 960M and that was fine for full HD gaming.
  18. hajime thread starter macrumors 601

    Jul 23, 2007
    Thanks. Actually 4K gaming is not the main thing. I like using large screen 4K monitor as the main monitor for productivity.

    I haven't done 4K gaming but it may be interesting to try.

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