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Single USB-C Cable For Everything?

E

eddjedi

macrumors 6502a
Original poster
Sep 7, 2011
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I've just bought a 13" MBP Touch Bar and one of the big attractions for me was having a single cable to connect for power, external display and external devices (I run two external USB 3.0 hard disks.)

I have been looking at the UltraFine 4K monitor as that does provide both display and power over a single cable, however reviews state the other USB-C ports are only USB 2.0 speed, and some people say this is due to physical bandwidth limitations of a single port.

So my question is hopefully fairly simple - is it possible to have power, external display, AND USB 3.0 hard disks running from a single cable with no drop in performance/power etc? Speed is important so if I need to use two cables I can, but would rather not.
 
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Yes this is true of the LG Ultrafine 4k, it utilizes the USB-C interface only, unlike the Ultrafine 5k model which supports the dual Thunderbolt 3/USB-C interface. A known limitation of the current 3.1 USB-C interface is that powering a 4k resolution will limit the bandwidth of the USB streams to USB 2.0-like speeds.

This may actually change at some point next year as certain devices may automatically be upgraded to USB-C 3.2; however the support for these free upgrades may be limited to a subset of devices (MacBooks) but not others (external monitors), depending on nothing more than the goodwill of the manufacturer: Apple or LG, in this example. Kind of hard to gauge.

What you can do and what I personally recommend is purchasing your own 4k/5k display along with a Thunderbolt 3 dock. The Elgato TB3 dock and the OWC TB3 dock seem to be among the favorites on these forums, along with a host of other options: Belkin, Kensington, Caldigit TS3... the list goes on.

This will allow for a true one-cable setup and will give you more flexibility in terms of which specific inputs you prioritize and exactly which display you want. For example, maybe you want a Firewire port or maybe you only require a $250 4k monitor and not a $500 monitor. In my opinion, the quality of the Ultrafine models is somewhat overkill for a vast majority of users and I think you can get more bang for your buck purchasing a dock along with a display. I've found no display out there which has all of the built-in ports and flexibility which a TB3 dock provides.

I have an Elgato 3 TB3 dock running a 27-inch LG 27UD69 4k display, a vertical 24" Dell display, a Logitech unifying receiver, ethernet, a Samsung T3 drive, all while powering my 15" MBP over at 85W...all running over a single cable. I can appreciate it every time I plug in and it really is a cool demonstration of how powerful the TB3 interface is.
 
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Thanks for the detailed reply. So to summarise a single USB C port does have the bandwidth to handle all of those things, but that particular monitor doesn't. Will check out the hubs you have suggested.
 
Question - bear with me if my terminology is incorrect. eddjedi, I'm not trying to hijack but rather determine whether or not monitors/docks that support 10Gbps USB 3.1 SuperSpeed+ will correct the issue we are facing (or if the only option is to wait for USB 3.2 - which means hardware upgrades, or purchasing a TB3 dock like the CalDigit that leverages Thunderbolt 3.)

I understand we can run a display with 4K @ 30 Hz over USB-C and get USB 3.1 data transfer speeds because the DisplayPort-over-USB-C stream does NOT occupy all of the SuperSpeed linked pairs.

I also understand the reason running 4k @ 60 Hz over USB-C (at least in regards to cables + devices that support only 3.1 gen 1) causes data transfers to revert to USB 2.0 specification is because the DisplayPort stream is occupying all of the four SuperSpeed linked pairs, forcing the data transfer to revert to the High Speed linked pair, and, consequently, resulting in USB 2.0 speeds.

I understand (on a non-technical level) that the shift from USB 3.1 gen 1 (SuperSpeed 5 Gbps) to USB 3.1 gen 2 (SuperSpeedPlus 10 Gbps) is due to a variety of efficiency changes, such as encoding and error correction - but also that the same total physical number of SS and HS pairs are used. However, does any of the efficiency changes also apply to this DisplayPort steam? (DisplayPort group notes the data structures of DP is similar to that of USB) - or does this only apply to data transfers independent of the DP over C? In other terms, will USB 3.1 gen 2 allow a 4k @ 60 hz DisplayPort stream -AND- USB 3.1 transfer speeds, or will the DisplayPort stream still occupy all of the SuperSpeed linked pairs, resulting in the same USB 2.0 transfer speeds?
 
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Yes you may be right, I've yet to find a dock that promises USB 3.0 and 60hz 4k, they all state 30hz...
 
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I understand the different protocol, but from what I've read the only extra thing TB3 seems to give over a single cable USB-C setup is 60hz 4k. Otherwise a USB 3 hub can do exactly the same thing.
 
eddjedi said:
I understand the different protocol, but from what I've read the only extra thing TB3 seems to give over a single cable USB-C setup is 60hz 4k. Otherwise a USB 3 hub can do exactly the same thing.
Click to expand...

USB 3 only has a 5gb/s bandwidth for everything you want to go over that one cable, TB 3 has 40gb/s.
 
eddjedi said:
I understand the different protocol, but from what I've read the only extra thing TB3 seems to give over a single cable USB-C setup is 60hz 4k. Otherwise a USB 3 hub can do exactly the same thing.
Click to expand...
Thunderbolt is a whole bus in itself. It can connect to PCI-E it's not a simple controller like USB. The chips are more complex and expensive.
 
OK thanks, I don't have a 4k monitor (yet) so have bought a Dodocool USB C hub which apparently supports power delivery, will report back.
 
Update, I bought this USB-C hub and USB-C extension cable:

https://www.amazon.co.uk/gp/product/B073WBJSG4/
https://www.amazon.co.uk/gp/product/B01FM4ZWV0/

For some reason none of the manufacturers seem to have realised that not everybody wants the hub on their desk, so as none have a USB-C input rather than a short built-in cable, I bought the extension cable. Thankfully it works perfectly, I am running a 1080p HDMI monitor, 2 x USB 3.0 external drives, power and ethernet all from a single cable with the hub neatly hidden behind my desk. No drops in speed or display quality due to the extension cable.

Total cost of under £50, I highly recmommend this combination if you don't need 4k and don't want to spend £200+ on a TB3 dock. Oh, and don't want an ugly hub with 5+ wires hanging out of it right next to your Mac :)
 
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