12 ms·

Explaining 4K 60Hz Video Through USB-C Hub (2019)

158 points by WayToDoor 5y ago

jbverschoor 5y ago
In other words, it's a big mess.
- mnd999 5y ago
  Everything involving a USB-C cable seems to have been a big mess since day 1. The argument for having the same connector for everything only works when you can plug in a cable and it just works. If I need special cables and capabilities for this, that and the other let’s just go back to having different cables so it’s at least obvious when we’ve got it wrong.
  - notJim 5y ago
    I disagree strongly, although I'm sympathetic. Yes it took far more research than ideal, but I have a TB3 dock currently charging my computer, connecting a mess of USB peripherals and connecting to my 4k monitor at 60 hz using only one single cable and port, and it's wonderful. Totally worth it.
    - minikites 5y ago
      How reliable is it? Everyone I know where I work has problems with their Thunderbolt breakout boxes.
      - btgeekboy 5y ago
        I have an OWC Thunderbolt 3 Pro dock; I use it with my work-issued 16" MBP and 2020 MBA. I have a 1440p and a 4K screen attached; both running at 60Hz. It was rough at first when I picked it up last year. However the driver updates in Big Sur seem to have fixed my complaints, particularly with the MBA that almost never worked. It works pretty well now. I unplug my work laptop and swap it for my personal one when I want to work on personal projects, and things just work. My biggest complaints about this dock now are that the fan is loud, and it only charges at 60w. I worked around the noise by attaching it to the underside of my desk, so it's pretty hard to hear now.
      - filoleg 5y ago
        Not the person you are replying to, but I've been using a Belkin Thunderbolt 3 Dock Pro for the past year, and can only claim positive experiences. No reliability issues whatsoever, despite me switching the dock between my work laptop and a personal laptop almost daily. The dock is connected to a bunch of peripherals, as well as 2 external monitors (one 1080p, another 4k@60hz). Only one cable going out of my laptop (connecting the laptop and the dock, as the cable connecting to the dock also charges the laptop at the same time).
        reportingsjr 5y ago
        I have the same experience with the dell usb c dock I use at work. Two 1080p external monitors, ethernet, usb hub, and I've never had a single issue with it.
      - notJim 5y ago
        Been using a CalDigit dock with two 2017 Macbook Pros (one work, one personal), basically zero problems. There was a slight hitch with the ethernet port when I first started, but it wasn't hard to fix.
  - Ashanmaril 5y ago
    Yeah, I remember being excited at the beginning thinking we finally had one cable to rule them all. Now we're a few years in and seeing a USB-C port just fills me with dread cause I know I'm gonna have to do research. And I yearn for the days where if I'm hooking up a monitor or something, I see an HDMI port and know exactly what that port is for and what kind of cable plugs into it. Seeing a USB-C port in something could mean any number of things.
bombcar 5y ago
What's annoying is that the "Thunderbolt" connectors ALSO depend on the chipset internally (and how it is routed) - for example on my MacBook Pro (15-inch, 2017) - I can drive four external monitors but ONLY if I connect two on each side of the laptop. I have two daisy chained via Thunderbolt but I cannot use that second Thunderbolt port on that side for a third monitor - it must be on the other side.
- pinot 5y ago
  At least you have USB-C on both sides. Dell is shipping 'professional' laptops with USB-C on only one side.
  - fireattack 5y ago
    But does it have the problem GP is describing? If not, I'd say it's definitely better than his/her MacBook Pro since they're at least functioning.
- AceJohnny2 5y ago
  If I understand your issue correctly, this is a macOS issue, where macOS only support DP daisy-chain (MST "Multi-Stream Transport") for mirroring content, not multiple screens. https://medium.com/@sebvance/everything-you-need-to-know-about-macbook-pros-and-their-lack-of-displayport-mst-multi-stream-98ce33d64af4 https://medium.com/@sebvance/everything-you-need-to-know-abo... (I stumbled upon this limitation myself recently. Supposedly Windows doesn't have this limitation though I haven't tried it myself)
  - bombcar 5y ago
    I don't know what I'm technically using, but it's two monitors daisy-chained via Thunderbolt and they're not mirrored. System Report says "Thunderbolt 2" is how they're connected.
    - paco3346 5y ago
      Part of it may also depend on the dock and how it routes the TB lanes. My dock uses 2 lanes for dock features and does passthrough for the rest. Are you able to daisy-chain your monitors off any of those ports without the dock in the path?
danieldk 5y ago
Be sure to read the update at the end, since the article is partly outdated with DisplayPort 1.4. With DP 1.4, only two lanes are necessary thanks to HBR3 (and DSC). So, you can have 4k@60Hz while also having USB 3.1 Gen3 at 10Gbit/s. E.g. I use a Lenovo USB-C Dock Gen 2, which supports this. You can have it all with just a single cable. Unfortunately, Linux misconfigures the lanes (does not use HBR3) for this hub and apparently some other hubs [1], so 4K@60Hz is not supported using a single cable. Windows 10 works fine and my wife's MacBook as well. [1] https://gitlab.freedesktop.org/drm/amd/-/issues/1317 https://gitlab.freedesktop.org/drm/amd/-/issues/1317
- Nextgrid 5y ago
  Does this require cable/hub support? I've currently got a hub which provides USB3 ports as well as HDMI, and as expected, only goes up to 4k@30Hz. Would a simple software change & hardware support on the host side be enough, or does the hub still need to be upgraded?
  - wmf 5y ago
    That hub presumably has a DP-to-HDMI chip that will never support DP 1.4. HDMI isn't for monitors anyway...
    - danieldk 5y ago
      It's so annoying that many monitors (e.g. common LG models) have 1x DP and 2x HDMI.
      - SECProto 5y ago
        I have a monitor with 1xDP and 2xHDMI and it's perfect. I use the DP for my desktop, one HDMI for my laptop dock, and the other HDMI for anything I might choose to use instead (console being the only thing I've used so far)
      - vladvasiliu 5y ago
        I have one of those LG monitors, although mine has a usb-c input which also handles display-port (so it's 2xDP + 2xHDMI). What really bugs me with HDMI is that monitors and computers never seem to agree on the image standard and for some reason always default to washed-out colours, even when connecting a PC to a PC monitor (as opposed to a TV). Under Linux/X11 I know how to set it in full range mode [0], but I was using such a monitor at home and connected it the HDMI output of my gaming PC (Radeon GPU) and couldn't figure out how to fix the washed-out colours. In the end I bit the bullet and bought a display-port switch. Now windows complains about the "limited display connectivity" (the monitor has a USB hub whose upstream is the usb-c/dp connector), but at least the colours look OK. --- [0] `xrandr --output HDMI1 --set "Broadcast RGB" "Full"` IIRC
deleted 5y ago
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- deleted 5y ago
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cwt137 5y ago
It would be interesting if the author mentioned not just about 4k60, but also how do you get something like 10bpp color. I have a MBP and can watch YouTube videos in HDR on the laptop screen, but not through the hub I have.
paco3346 5y ago
I struggled for a long time to find a "full featured" dock that could support my setup with a single cable. I wanted 3x 2560x1440@60 monitors, wired ethernet, USB 3.x, and power without having 5+ cables to move around. Last year Dell finally released the WD19TB and it's awesome. https://www.delltechnologies.com/resources/en-us/asset/data-sheets/products/electronics-accessories/dell_thunderbolt_dock_wd19tb_spec_sheet.pdf https://www.delltechnologies.com/resources/en-us/asset/data-... I happen to run an XPS with Arch & KDE Plasma and everything worked perfectly out of the box. Highly recommended for anyone who has a TB3 laptop and is looking for a good dock.
- baybal2 5y ago
  The problem with TB used to be the power consumption of the PHY chip. A guy in a coworking next to me has a Dell dock which makes his fans spin, and the laptop body painfully hot to touch. How is it for you?
  - paco3346 5y ago
    Mine stays warmish but not enough to make the fans consistently spin. The heat generated by using the dock is no different than what's generated by using an AC adapter with individual DP & USB cables.
  - LeonM 5y ago
    This typical for laptops with discrete GPUs. Outputting video over TB can often only be done by the discrete GPU. I do not know the reason why this works this way. On my Lenovo X1E, this is also the case. Thunderbolt video output only works via the nVidia GPU (instead of the Intel graphics on the CPU). So connecting the TB dock causes my fans to spin up, as the laptop is now rendering my desktop using a power hungry nVidia chip.
  - StringyBob 5y ago
    This is still noticeable in lower power devices. I have discovered that if I leave a usb cable plugged into a MacBook Air M1 usbc socket in standby, it draws about half a watt extra, even though the cable power draw is zero. This means the battery goes flat in a few days vs a few weeks in standby - the PHY seems to be using more power in standby than rest of laptop
ClumsyPilot 5y ago
I am trying to get usbc connection to work on 4k monitor, and i tried 5 different usbc cabkes, only one worked. Every week it falls back to 30 fps and needs to be replugged, caressed, and incantations
- minikites 5y ago
  I use HDMI and it works great. It's hard to see USB-C as anything but a failure for devices other than smartphones/tablets.
- danieldk 5y ago
  I have two of these. They always work without any issues: https://www.coolblue.nl/en/product/723407/startech-usb-c-to-displayport-cable-1-meter.html https://www.coolblue.nl/en/product/723407/startech-usb-c-to-...
- radicality 5y ago
  Something similar happens to me often with a Dell monitor and MacBook Pro over usb-c. What I need to do is after the monitor turns on at 30Hz, turn off the monitor (don’t touch cable) and then turn back on. I know “have you tried turning it off and on” sounds ridiculous, but it always reliably brings me back to 60Hz.
minikites 5y ago
Remember when we had different connectors for different purposes and it was easy to tell what a given connector or cable did? I do, and I think USB-C is a massive backwards step in usability.
- ants_a 5y ago
  It didn't have to be. If only there was some foresight into standardizing a marking system to indicate capabilities of cables and ports. And possibly reduce the number of options available based on educated guesses on use cases and cost drivers. Right now there's no way to determine what voltages a PD port can supply, what voltages a device requires to be able to charge, what amperages each one is capable of handling, if the cable is capable of data, what data rates are supported, if a port can output video, which standards it can output in, and on and on and on. Instead of coming with the labeling genius that is USB 3.2 Gen 2x2 (pop quiz, is that better/worse/compatible with USB 4 3x1?), a marking scheme for capabilities would have been nice.
  - tzs 5y ago
    What would be really helpful is a doohickey that you can plug into a USB-C/TB port and it tries to negotiate all power options and data speeds and video modes, and then tells you which ones that port supports. Add another doohickey, or incorporate it into the first, that has two ports. You plug a cable into both, and it tells you what the cable supports.
  - minikites 5y ago
    How is all that an improvement over separate cable and port shapes?
_nickwhite 5y ago
I'm over IT for about 40 remote workers. One of the comments in this article rings so true about the pain of using USB-C to DisplayPort: "I hate my USB-C monitor ports that work is making me use. Sometimes when I plug the USB-Dock in, it works fine. Other times I get one of the two 1920×1080 monitors attached to turn on. Others, no monitors turn on, and I have to unplug it and plug it back in. Then it usually works." It's SUPER finicky and picky, pretty much across the board. I find this true for the PC/Windows- macbook pros seems to work MUCH better, even with triple-2k monitors, but still not perfectly every time.
- nikanj 5y ago
  I have a macbook and I’m sad to report it’s just as finicky
  - abhorrence 5y ago
    I think it depends a bit on the generation. I have a 15” MBP that inconsistently connects to the usb devices connected to the monitor. And I have a 16” 2019 one that has never failed to connect properly to the exact same setup. Of course there could be a different configuration of monitor and usb devices that my 16” would fail to work consistently with.
  - Rebelgecko 5y ago
    The problem I have with my MBP is that it randomly forgets which monitor is which, so the left one becomes the right and vice versa
- danieldk 5y ago
  It's interesting how experiences differ. For me, USB-C <-> DP has been super reliable for years - Mac, Linux, and Windows. Admittedly, that was with a USB-C <-> DP (Alt mode) cable without any other functions.
- vladvasiliu 5y ago
  This looks to me like the controllers are sometimes badly implemented. I have a HP ProBook with a USB-C/DP output that I plug into an LG monitor with a USB hub. The hub works in USB2 mode + 4K@60Hz (as advertised by LG). This has worked consistently for me for more than two years, using Arch Linux + X11. Sleep, plug, unplug whenever I like, it just works. It seems to also work fairly consistently when colleagues plug in their Windows laptops (also HP). I also have a HP EliteDesk with a Thunderbolt + USB-C / DP port. This is a shitshow. The same LG monitor works every time for BIOS and such when connected through USB-C. Installing Windows works. The Windows logon screen sometimes shows up, but not reliably. The Windows desktop has only ever worked once. This same setup usually works with Linux/X11. But after a display sleep, it sometimes figures it can only do 4K@30Hz. Sometimes it chooses some other random resolution. If I unplug it a number of times, it may end up working again. Maybe. Or maybe not. Sometimes I have to reboot. Which may or may not solve the issue. Plugging in a thunderbolt display (Apple) works more often. But if the screen goes to sleep, there's a good chance it will wake up with some ridiculous resolution, like 1280x720. It's impossible to change it. If the computer goes to sleep or if the monitor is unplugged, it's game over. The screen will never come back again unless I do a cold boot (turn off & on, reboot won't do). I keep hearing people complaining about macbooks being unreliable with external screens. I wonder if it isn't the same kind of issue with a broken controller implementation somewhere. I've never had the slightest issue with external screens on my 2013 MBP (15" with nvidia dGPU). Thunderbolt, 4k@60Hz, you name it, it works. Plug / unplug when it's running, when it's sleeping, whatever, it just works as expected.
philluminati 5y ago
I bought a usb-c dock earlier this week. "Selore 8 in 1" (£44) with a separate usb-c power charger and an extension cable (2 meter male to female usb-c cable) it seems to work great. Out of the box on Debian Stable. I installed autorandr and saved my laptop's solo profile and the preferred arrangement when I use the dock with my monitor and it's fantastic. I slap a single cable into my laptop when I plonk it on my desk and I get my monitor, keyboard, mouse autoconnect and my laptop starts charging too. This is the future I wanted for my home office arrangement. One cable does everything. I wish it were my office too The device does have some interesting small print like the article says, so it was an interesting read. 1 monitor = 4k @ 60hz, 2 monitors = 4k @ 30hz (It has 2xHDMI outputs) but you can have two monitors at 4k and 60hz IF they mirror each other too. Regardless, I'm happy with 1080p (always at 60hz) so it doesn't seem to affect me. I would recommend them even if the article does suggest they aren't quite as mature as they should be yet.
rsync 5y ago
What, specifically, does this imply for the number of external displays one can attach to a raspberry pi 4 ? Naively, you might think that with 2x USB-C ports, you could attach two of these: Cable Matters 201055 – 2x DisplayPort, power, ethernet, 2x USB2 ... and also attach something to each of the onboard HDMI port and have a total of six monitors. However, I don't think that's the case because of something-something-video lanes/memory/bios something-something ... Does anyone have a finer grained understanding ? EDIT: I am reminded that this post[1] discusses an alternate route using the CM4 and the pcie port on the breakout board ... and failing to succeed in using a pci graphics card. USB3 monitors seem a more promising avenue but, again, I think there is some memory/BAR limitation ... [1] https://www.jeffgeerling.com/blog/2020/external-gpus-and-raspberry-pi-compute-module-4 https://www.jeffgeerling.com/blog/2020/external-gpus-and-ras...
- nfriedly 5y ago
  For a Raspberry Pi 4B, the USB-C port does not support displays, only power and USB 2.0 data. The other pins are not connected to anything. Without extra hardware, you can only connect displays to the two microHDMI ports.
  - rsync 5y ago
    There are, however, the two USB3 ports which you'd think could be used to drive displays ... I believe they cannot be, however.
    - ddalex 5y ago
      Only DisplayLink... but I've tried to compile the DisplayLink drivers for Pi4 for my adapter and failed miserably.
- deleted 5y ago
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rozularen 5y ago
With the following constraints how would one manage to have the less amount of cable dangling around? 1 PC (personal use, desktop or laptop) 1 work laptop 2 Monitors Keyboard & Mouse Be able to connect the work laptop with only 1 cable and switch keyboard mouse and monitors to it Maybe should I look for a KVM switch instead?
- sp332 5y ago
  You could use a wireless mouseand keyboard that support being connected to multiple computers. I have a Logitech MX Anywhere mouse that works really well, and I know there are keyboards that do that too.
- throwaway789394 5y ago
  I remote into my work laptop from my desktop. Works like a charm.
- cephalization 5y ago
  I would look into usb switcher for peripherals and dock for the laptop. Manually change displays using on screen controls. Having video switching gets real expensive and only a few KVMs support high refresh / high resolution displays.
- bradstewart 5y ago
  Is there an additional constraint to "not unplug things from your personal machine"? If not, and you can get two machines with Thunderbolt, a TB dock solves this. I have my monitors, keyboard, mouse, ethernet, etc all plugged into a TB docking station. Then a single TB cable I swap between my work machine (Macbook Pro) and personal machine (Razer Blade).
- dracodoc 5y ago
  My setup is a little different but it's reliable and simple: Dell UltraSharp U3417W has built in usb hub. I can connect pc and laptop to this monitor and switch between them with monitor button. Connect keyboard and mouse to monitor (and connect upstream usb cable to pc/laptop) so your keyboard and mouse move with your monitor switch. This setup only use one monitor but it's enough for my use. I have another regular 1080p monitor that always connect to one machine.
anyfoo 5y ago
Relatedly, does anyone have any solution for switching a 5k LG monitor between two Macs? There seems to be only a single KVM switch that does that, and it's around $500. It also does not switch one Thunderbolt, but two Display Ports, so it seems that you would additionally need a bunch of adapters which split the USB-C Thunderbolt cable into two Display Port connections, and back together at the other end. Note that there seem to be more solutions for 4k, but it's my understanding that those don't work for 5k.
- perryh2 5y ago
  If you aren't switching between your computers too often, you can just get a USB hub like this and switch between display inputs from your monitor: https://www.amazon.com/gp/product/B083JKDNRJ/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 https://www.amazon.com/gp/product/B083JKDNRJ/ref=ppx_yo_dt_b...
  - anyfoo 5y ago
    My monitor only has a single input, that's the problem I'm trying to solve. I don't need to switch USB.
- ggayan 5y ago
  Use a DP 1.4 switch: https://www.amazon.com/Angusplay-DisplayPort-Switch-Bidirectional-Splitter/dp/B089SLDDZZ/ref=sr_1_3?dchild=1&keywords=thunderbolt+switch&qid=1619119846&sr=8-3 https://www.amazon.com/Angusplay-DisplayPort-Switch-Bidirect... I tried ConnectPro's DP 1.4 KVM and the display blacked out constantly in MacOS. Friends who purchased the same KVM ran into the same issue with displays that push DP spec to the limit like 3440x1440@144. The switch I shared works just fine. From time to time (once every 1-2 months maybe) the display blacks out for a second but a computer restart does the trick, or reconnecting cables. Also make sure to get HBR3 displayport certified cables.
  - anyfoo 5y ago
    Just to confirm, this does work with LG 5k monitors? The resolution there is 5120x2880, which is significantly more (the vertical resolution alone is doubled, and then some for the horizontal), but I don't know the refresh rate, so the bandwidth could still be similar maybe. EDIT: I'm also wondering, the only switch I know to be working uses two display port cables to the monitor (which I'd have to adapt to one Thunderbolt 3 instead), while your device only uses one. That doesn't bode well...
Camillo 5y ago
If you're buying a hub now, you don't want any of these things, you want Thunderbolt 4. I'd really like to see an equivalent article for it.
Dylan16807 5y ago
> DisplayPort 1.4 can deliver 4K 60Hz video using only two lanes, with a new high-bit-rate mode called HBR3 with a compression mode called DSC. This makes it possible to get 4K60 video and USB 3.1 ports in the same hub, but only if the computer, hub, and monitor all support DisplayPort 1.4 and HBR3. You don't need DSC to display 4K60 over two lanes, only to go above that or add HDR too. Also displayport 1.4 support doesn't guarantee DSC for some reason.
z9qjk 5y ago
I think the whole concept of usb c/tb3 is flawed, cables should be inside the computer not outside. I have a fairly simple setup: 2017 Macbook Pro with two TB3 ports, a Dell monitor, an external SSD, a TB2 soundcard and a wireless usb mouse, because a traditional mouse works better in VMs than a Magic Mouse. This setup worked perfectly with a 2015 13" MBP: the HDMI port supports the Dell monitor, I connected my soundcard to the dedicated TB2 port and I still had two USB3 ports for my mouse and the external ssd. Now comes the revolutionized & courageous setup with two TB3 ports: First of all I had to buy a USB3 dock. That's ok but still 50 euros down the toilet. Then an Apple issued TB2-TB3 adapter which was another 100 euros. But then I figured I can't connect these devices at once so I've had to buy an Apple Issued Digital AV Adapter for another 100 euros. We are already at 250 euros and the fun part just starts: If I connect my Dell monitor and my soundcard (even turned off) at the same time the monitor starts to flicker and the soundcard starts spitting out dirty electrostatic noise. Yes, a good old ground loop! So now I can't listen to music with my soundcard and have my monitor plugged in at the same time. I can't use my wireless mouse because the wireless dongle is too far from my USB3 dock. I can't use my external ssd reliably because every time I put my Macbook to sleep it disconnects in a way that i have to phisically reconnect it. Every fkn time. So I thought, gee I just have to shell out another 300 euros for a Caldigit TS3+ and all my problems will be solved, right? USB-C ecosystem: hold my beer The statical noise comes through the TS3+ as well plus it heats up my Macbook to a completely pathetic degree, so it throttles. Because it has to be thin too. TDP is just stat for nerds. SSD is still unreliable and the dock is still too far from my mouse to have a stable connection. In the end I spent 550 euros on completely useless environmental waste bullsh*t that shouldn't exist at all. I get what Apple and the whole industry had in mind with usb-c but it is flawed by design. It has to be reengineered from the ground up.
- qihqi 5y ago
  Hope you don't speak Spanish and can enjoy this one: https://www.youtube.com/watch?v=-I9n-cjl7zg https://www.youtube.com/watch?v=-I9n-cjl7zg
GekkePrutser 5y ago
Aha. Now I understand why my Lenovo USB-C dock doesn't do 4K@60 on my Mac. It's not thunderbolt capable. By the way, it does have an extra limitation on Mac. It only supports one external display. Apparently this is due to the Mac lacking support for Multi Stream Technology over DisplayPort (because it has Thunderbolt instead). Unfortunately Thunderbolt hubs are very expensive as the article also mentions. So I added a DisplayLink adapter for my third display (one 4K@60 directly connected to a USB-C port, the hub on the other with one HDMI out and the display link and lots of other USB stuff :) ) By the way DisplayLink support is pretty good now on Mac. Even for the new chipsets. I wouldn't call it nonexistent as the article does. It does have some limitations though, like Night Light not switching on.
- JoBrad 5y ago
  The M1 laptops don’t support more than 1 external display, either. Same laptop with Intel chip does, though.
- rahimnathwani 5y ago
  "Apparently this is due to the Mac lacking support for Multi Stream Technology over DisplayPort" AIUI it's not the Mac (hardware) that lacks this support, but the operating system (MacOS). Running Windows on the same hardware will allow you to use two monitors.
protoman3000 5y ago
Yeah, USB C is a mess and Thunderbolt 3 is obviously the superior 1-cable technology. Unfortunately, though, Thunderbolt 3 is a piece of sh*t, too [1] [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1766076 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1766076
steveBK123 5y ago
TB3/USBC is insane and a mess. Whoever decided to use the same connector is insane. I have varying cables with the same connector which do: - Power but not data - USB Data but no/low power - USB Data but only at USB2 speed (why?) - USB Data but only USB3 - TB3 - LOL don't forget USB-PD At least in the late 90s ecosystem of a dozen different connectors you could visually identify them. Now I have various special unicorn cables around the house which look the same, but only work for use case X or Y or Z. Examples are things like - I have one cable that can charge my camera over USB-C, and one cable that can transmit data between my camera & MacBook.. but neither does both. I suppose I could acquire a third cable to accomplish that.
- xenadu02 5y ago
  This is a feature, not a bug. The USB-IF is just a bunch of manufacturers getting together to agree on a standard. The vast majority of them are interested in one thing: lowering the BOM. Cheap, cheap, cheap! That's what matters. Making things super cheap means making lots of the spec optional so they can re-use existing chip designs, less expensive cables, etc. If they can make things easier for customers that's a nice bonus but ultimately it doesn't matter. The free market does not always optimize for what you think it should optimize for.
- vetinari 5y ago
  Have look at the USB-C pinout, it will be obvious then. (E.g.: https://www.allaboutcircuits.com/technical-articles/introduction-to-usb-type-c-which-pins-power-delivery-data-transfer/ https://www.allaboutcircuits.com/technical-articles/introduc...) Wrt USB2 vs USB3 - these have separate pins and wires. USB3 requires four extra wires, which must be of higher quality than those for USB2; their presence is the difference between 2 EUR and 10 EUR cable. TB3 is quite different cable; if it is over 0.5m, it will be an active one.
posobin 5y ago
Previous discussion of this post (2019, 171 comments): https://news.ycombinator.com/item?id=21532795 https://news.ycombinator.com/item?id=21532795 It has also been mentioned in 10 other HN comment threads. Found via https://ampie.app/url-context https://ampie.app/url-context.
adamparsons 5y ago
It blew my mind the other day when work gave us one of Apple's hdmi/usb/charge multiport adapters, that it could power 4k60 and a USB3 port without using thunderbolt under the hood. It was my understanding its either 4k60 with no usb, or 4k30 with usb. I'm assuming its using this newfangled HBR3 under the hood, or perhaps it actually is using thunderbolt secretly.
- rahimnathwani 5y ago
  If you're talking about the "USB-C Digital AV Multiport Adapter", the product page lists which Macbooks can do 4k60, and which can only do 1080p60/4k30. Those which can do 4k60 all support TB3, so I'm guessing it uses Thunderbolt to achieve this.

158 points by WayToDoor 5y ago

jbverschoor 5y ago

In other words, it's a big mess.

mnd999 5y ago
Everything involving a USB-C cable seems to have been a big mess since day 1. The argument for having the same connector for everything only works when you can plug in a cable and it just works. If I need special cables and capabilities for this, that and the other let’s just go back to having different cables so it’s at least obvious when we’ve got it wrong.
- notJim 5y ago
  I disagree strongly, although I'm sympathetic. Yes it took far more research than ideal, but I have a TB3 dock currently charging my computer, connecting a mess of USB peripherals and connecting to my 4k monitor at 60 hz using only one single cable and port, and it's wonderful. Totally worth it.
  - minikites 5y ago
    How reliable is it? Everyone I know where I work has problems with their Thunderbolt breakout boxes.
    - btgeekboy 5y ago
      I have an OWC Thunderbolt 3 Pro dock; I use it with my work-issued 16" MBP and 2020 MBA. I have a 1440p and a 4K screen attached; both running at 60Hz. It was rough at first when I picked it up last year. However the driver updates in Big Sur seem to have fixed my complaints, particularly with the MBA that almost never worked. It works pretty well now. I unplug my work laptop and swap it for my personal one when I want to work on personal projects, and things just work. My biggest complaints about this dock now are that the fan is loud, and it only charges at 60w. I worked around the noise by attaching it to the underside of my desk, so it's pretty hard to hear now.
    - filoleg 5y ago
      Not the person you are replying to, but I've been using a Belkin Thunderbolt 3 Dock Pro for the past year, and can only claim positive experiences. No reliability issues whatsoever, despite me switching the dock between my work laptop and a personal laptop almost daily. The dock is connected to a bunch of peripherals, as well as 2 external monitors (one 1080p, another 4k@60hz). Only one cable going out of my laptop (connecting the laptop and the dock, as the cable connecting to the dock also charges the laptop at the same time).
      - reportingsjr 5y ago
        I have the same experience with the dell usb c dock I use at work. Two 1080p external monitors, ethernet, usb hub, and I've never had a single issue with it.
    - notJim 5y ago
      Been using a CalDigit dock with two 2017 Macbook Pros (one work, one personal), basically zero problems. There was a slight hitch with the ethernet port when I first started, but it wasn't hard to fix.
- Ashanmaril 5y ago
  Yeah, I remember being excited at the beginning thinking we finally had one cable to rule them all. Now we're a few years in and seeing a USB-C port just fills me with dread cause I know I'm gonna have to do research. And I yearn for the days where if I'm hooking up a monitor or something, I see an HDMI port and know exactly what that port is for and what kind of cable plugs into it. Seeing a USB-C port in something could mean any number of things.

bombcar 5y ago

What's annoying is that the "Thunderbolt" connectors ALSO depend on the chipset internally (and how it is routed) - for example on my MacBook Pro (15-inch, 2017) - I can drive four external monitors but ONLY if I connect two on each side of the laptop. I have two daisy chained via Thunderbolt but I cannot use that second Thunderbolt port on that side for a third monitor - it must be on the other side.

pinot 5y ago
At least you have USB-C on both sides. Dell is shipping 'professional' laptops with USB-C on only one side.
- fireattack 5y ago
  But does it have the problem GP is describing? If not, I'd say it's definitely better than his/her MacBook Pro since they're at least functioning.
AceJohnny2 5y ago
If I understand your issue correctly, this is a macOS issue, where macOS only support DP daisy-chain (MST "Multi-Stream Transport") for mirroring content, not multiple screens. https://medium.com/@sebvance/everything-you-need-to-know-about-macbook-pros-and-their-lack-of-displayport-mst-multi-stream-98ce33d64af4 https://medium.com/@sebvance/everything-you-need-to-know-abo... (I stumbled upon this limitation myself recently. Supposedly Windows doesn't have this limitation though I haven't tried it myself)
- bombcar 5y ago
  I don't know what I'm technically using, but it's two monitors daisy-chained via Thunderbolt and they're not mirrored. System Report says "Thunderbolt 2" is how they're connected.
  - paco3346 5y ago
    Part of it may also depend on the dock and how it routes the TB lanes. My dock uses 2 lanes for dock features and does passthrough for the rest. Are you able to daisy-chain your monitors off any of those ports without the dock in the path?

danieldk 5y ago

Be sure to read the update at the end, since the article is partly outdated with DisplayPort 1.4. With DP 1.4, only two lanes are necessary thanks to HBR3 (and DSC). So, you can have 4k@60Hz while also having USB 3.1 Gen3 at 10Gbit/s. E.g. I use a Lenovo USB-C Dock Gen 2, which supports this. You can have it all with just a single cable. Unfortunately, Linux misconfigures the lanes (does not use HBR3) for this hub and apparently some other hubs [1], so 4K@60Hz is not supported using a single cable. Windows 10 works fine and my wife's MacBook as well. [1] https://gitlab.freedesktop.org/drm/amd/-/issues/1317 https://gitlab.freedesktop.org/drm/amd/-/issues/1317

Nextgrid 5y ago
Does this require cable/hub support? I've currently got a hub which provides USB3 ports as well as HDMI, and as expected, only goes up to 4k@30Hz. Would a simple software change & hardware support on the host side be enough, or does the hub still need to be upgraded?
- wmf 5y ago
  That hub presumably has a DP-to-HDMI chip that will never support DP 1.4. HDMI isn't for monitors anyway...
  - danieldk 5y ago
    It's so annoying that many monitors (e.g. common LG models) have 1x DP and 2x HDMI.
    - SECProto 5y ago
      I have a monitor with 1xDP and 2xHDMI and it's perfect. I use the DP for my desktop, one HDMI for my laptop dock, and the other HDMI for anything I might choose to use instead (console being the only thing I've used so far)
    - vladvasiliu 5y ago
      I have one of those LG monitors, although mine has a usb-c input which also handles display-port (so it's 2xDP + 2xHDMI). What really bugs me with HDMI is that monitors and computers never seem to agree on the image standard and for some reason always default to washed-out colours, even when connecting a PC to a PC monitor (as opposed to a TV). Under Linux/X11 I know how to set it in full range mode [0], but I was using such a monitor at home and connected it the HDMI output of my gaming PC (Radeon GPU) and couldn't figure out how to fix the washed-out colours. In the end I bit the bullet and bought a display-port switch. Now windows complains about the "limited display connectivity" (the monitor has a USB hub whose upstream is the usb-c/dp connector), but at least the colours look OK. --- [0] `xrandr --output HDMI1 --set "Broadcast RGB" "Full"` IIRC

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cwt137 5y ago

It would be interesting if the author mentioned not just about 4k60, but also how do you get something like 10bpp color. I have a MBP and can watch YouTube videos in HDR on the laptop screen, but not through the hub I have.

paco3346 5y ago

I struggled for a long time to find a "full featured" dock that could support my setup with a single cable. I wanted 3x 2560x1440@60 monitors, wired ethernet, USB 3.x, and power without having 5+ cables to move around. Last year Dell finally released the WD19TB and it's awesome. https://www.delltechnologies.com/resources/en-us/asset/data-sheets/products/electronics-accessories/dell_thunderbolt_dock_wd19tb_spec_sheet.pdf https://www.delltechnologies.com/resources/en-us/asset/data-... I happen to run an XPS with Arch & KDE Plasma and everything worked perfectly out of the box. Highly recommended for anyone who has a TB3 laptop and is looking for a good dock.

baybal2 5y ago
The problem with TB used to be the power consumption of the PHY chip. A guy in a coworking next to me has a Dell dock which makes his fans spin, and the laptop body painfully hot to touch. How is it for you?
- paco3346 5y ago
  Mine stays warmish but not enough to make the fans consistently spin. The heat generated by using the dock is no different than what's generated by using an AC adapter with individual DP & USB cables.
- LeonM 5y ago
  This typical for laptops with discrete GPUs. Outputting video over TB can often only be done by the discrete GPU. I do not know the reason why this works this way. On my Lenovo X1E, this is also the case. Thunderbolt video output only works via the nVidia GPU (instead of the Intel graphics on the CPU). So connecting the TB dock causes my fans to spin up, as the laptop is now rendering my desktop using a power hungry nVidia chip.
- StringyBob 5y ago
  This is still noticeable in lower power devices. I have discovered that if I leave a usb cable plugged into a MacBook Air M1 usbc socket in standby, it draws about half a watt extra, even though the cable power draw is zero. This means the battery goes flat in a few days vs a few weeks in standby - the PHY seems to be using more power in standby than rest of laptop

ClumsyPilot 5y ago

I am trying to get usbc connection to work on 4k monitor, and i tried 5 different usbc cabkes, only one worked. Every week it falls back to 30 fps and needs to be replugged, caressed, and incantations

minikites 5y ago
I use HDMI and it works great. It's hard to see USB-C as anything but a failure for devices other than smartphones/tablets.
danieldk 5y ago
I have two of these. They always work without any issues: https://www.coolblue.nl/en/product/723407/startech-usb-c-to-displayport-cable-1-meter.html https://www.coolblue.nl/en/product/723407/startech-usb-c-to-...
radicality 5y ago
Something similar happens to me often with a Dell monitor and MacBook Pro over usb-c. What I need to do is after the monitor turns on at 30Hz, turn off the monitor (don’t touch cable) and then turn back on. I know “have you tried turning it off and on” sounds ridiculous, but it always reliably brings me back to 60Hz.

minikites 5y ago

Remember when we had different connectors for different purposes and it was easy to tell what a given connector or cable did? I do, and I think USB-C is a massive backwards step in usability.

ants_a 5y ago
It didn't have to be. If only there was some foresight into standardizing a marking system to indicate capabilities of cables and ports. And possibly reduce the number of options available based on educated guesses on use cases and cost drivers. Right now there's no way to determine what voltages a PD port can supply, what voltages a device requires to be able to charge, what amperages each one is capable of handling, if the cable is capable of data, what data rates are supported, if a port can output video, which standards it can output in, and on and on and on. Instead of coming with the labeling genius that is USB 3.2 Gen 2x2 (pop quiz, is that better/worse/compatible with USB 4 3x1?), a marking scheme for capabilities would have been nice.
- tzs 5y ago
  What would be really helpful is a doohickey that you can plug into a USB-C/TB port and it tries to negotiate all power options and data speeds and video modes, and then tells you which ones that port supports. Add another doohickey, or incorporate it into the first, that has two ports. You plug a cable into both, and it tells you what the cable supports.
- minikites 5y ago
  How is all that an improvement over separate cable and port shapes?

_nickwhite 5y ago

I'm over IT for about 40 remote workers. One of the comments in this article rings so true about the pain of using USB-C to DisplayPort: "I hate my USB-C monitor ports that work is making me use. Sometimes when I plug the USB-Dock in, it works fine. Other times I get one of the two 1920×1080 monitors attached to turn on. Others, no monitors turn on, and I have to unplug it and plug it back in. Then it usually works." It's SUPER finicky and picky, pretty much across the board. I find this true for the PC/Windows- macbook pros seems to work MUCH better, even with triple-2k monitors, but still not perfectly every time.

nikanj 5y ago
I have a macbook and I’m sad to report it’s just as finicky
- abhorrence 5y ago
  I think it depends a bit on the generation. I have a 15” MBP that inconsistently connects to the usb devices connected to the monitor. And I have a 16” 2019 one that has never failed to connect properly to the exact same setup. Of course there could be a different configuration of monitor and usb devices that my 16” would fail to work consistently with.
- Rebelgecko 5y ago
  The problem I have with my MBP is that it randomly forgets which monitor is which, so the left one becomes the right and vice versa
danieldk 5y ago
It's interesting how experiences differ. For me, USB-C <-> DP has been super reliable for years - Mac, Linux, and Windows. Admittedly, that was with a USB-C <-> DP (Alt mode) cable without any other functions.
vladvasiliu 5y ago
This looks to me like the controllers are sometimes badly implemented. I have a HP ProBook with a USB-C/DP output that I plug into an LG monitor with a USB hub. The hub works in USB2 mode + 4K@60Hz (as advertised by LG). This has worked consistently for me for more than two years, using Arch Linux + X11. Sleep, plug, unplug whenever I like, it just works. It seems to also work fairly consistently when colleagues plug in their Windows laptops (also HP). I also have a HP EliteDesk with a Thunderbolt + USB-C / DP port. This is a shitshow. The same LG monitor works every time for BIOS and such when connected through USB-C. Installing Windows works. The Windows logon screen sometimes shows up, but not reliably. The Windows desktop has only ever worked once. This same setup usually works with Linux/X11. But after a display sleep, it sometimes figures it can only do 4K@30Hz. Sometimes it chooses some other random resolution. If I unplug it a number of times, it may end up working again. Maybe. Or maybe not. Sometimes I have to reboot. Which may or may not solve the issue. Plugging in a thunderbolt display (Apple) works more often. But if the screen goes to sleep, there's a good chance it will wake up with some ridiculous resolution, like 1280x720. It's impossible to change it. If the computer goes to sleep or if the monitor is unplugged, it's game over. The screen will never come back again unless I do a cold boot (turn off & on, reboot won't do). I keep hearing people complaining about macbooks being unreliable with external screens. I wonder if it isn't the same kind of issue with a broken controller implementation somewhere. I've never had the slightest issue with external screens on my 2013 MBP (15" with nvidia dGPU). Thunderbolt, 4k@60Hz, you name it, it works. Plug / unplug when it's running, when it's sleeping, whatever, it just works as expected.

philluminati 5y ago

I bought a usb-c dock earlier this week. "Selore 8 in 1" (£44) with a separate usb-c power charger and an extension cable (2 meter male to female usb-c cable) it seems to work great. Out of the box on Debian Stable. I installed autorandr and saved my laptop's solo profile and the preferred arrangement when I use the dock with my monitor and it's fantastic. I slap a single cable into my laptop when I plonk it on my desk and I get my monitor, keyboard, mouse autoconnect and my laptop starts charging too. This is the future I wanted for my home office arrangement. One cable does everything. I wish it were my office too The device does have some interesting small print like the article says, so it was an interesting read. 1 monitor = 4k @ 60hz, 2 monitors = 4k @ 30hz (It has 2xHDMI outputs) but you can have two monitors at 4k and 60hz IF they mirror each other too. Regardless, I'm happy with 1080p (always at 60hz) so it doesn't seem to affect me. I would recommend them even if the article does suggest they aren't quite as mature as they should be yet.

rsync 5y ago

What, specifically, does this imply for the number of external displays one can attach to a raspberry pi 4 ? Naively, you might think that with 2x USB-C ports, you could attach two of these: Cable Matters 201055 – 2x DisplayPort, power, ethernet, 2x USB2 ... and also attach something to each of the onboard HDMI port and have a total of six monitors. However, I don't think that's the case because of something-something-video lanes/memory/bios something-something ... Does anyone have a finer grained understanding ? EDIT: I am reminded that this post[1] discusses an alternate route using the CM4 and the pcie port on the breakout board ... and failing to succeed in using a pci graphics card. USB3 monitors seem a more promising avenue but, again, I think there is some memory/BAR limitation ... [1] https://www.jeffgeerling.com/blog/2020/external-gpus-and-raspberry-pi-compute-module-4 https://www.jeffgeerling.com/blog/2020/external-gpus-and-ras...

nfriedly 5y ago
For a Raspberry Pi 4B, the USB-C port does not support displays, only power and USB 2.0 data. The other pins are not connected to anything. Without extra hardware, you can only connect displays to the two microHDMI ports.
- rsync 5y ago
  There are, however, the two USB3 ports which you'd think could be used to drive displays ... I believe they cannot be, however.
  - ddalex 5y ago
    Only DisplayLink... but I've tried to compile the DisplayLink drivers for Pi4 for my adapter and failed miserably.
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rozularen 5y ago

With the following constraints how would one manage to have the less amount of cable dangling around? 1 PC (personal use, desktop or laptop) 1 work laptop 2 Monitors Keyboard & Mouse Be able to connect the work laptop with only 1 cable and switch keyboard mouse and monitors to it Maybe should I look for a KVM switch instead?

sp332 5y ago
You could use a wireless mouseand keyboard that support being connected to multiple computers. I have a Logitech MX Anywhere mouse that works really well, and I know there are keyboards that do that too.
throwaway789394 5y ago
I remote into my work laptop from my desktop. Works like a charm.
cephalization 5y ago
I would look into usb switcher for peripherals and dock for the laptop. Manually change displays using on screen controls. Having video switching gets real expensive and only a few KVMs support high refresh / high resolution displays.
bradstewart 5y ago
Is there an additional constraint to "not unplug things from your personal machine"? If not, and you can get two machines with Thunderbolt, a TB dock solves this. I have my monitors, keyboard, mouse, ethernet, etc all plugged into a TB docking station. Then a single TB cable I swap between my work machine (Macbook Pro) and personal machine (Razer Blade).
dracodoc 5y ago
My setup is a little different but it's reliable and simple: Dell UltraSharp U3417W has built in usb hub. I can connect pc and laptop to this monitor and switch between them with monitor button. Connect keyboard and mouse to monitor (and connect upstream usb cable to pc/laptop) so your keyboard and mouse move with your monitor switch. This setup only use one monitor but it's enough for my use. I have another regular 1080p monitor that always connect to one machine.

anyfoo 5y ago

Relatedly, does anyone have any solution for switching a 5k LG monitor between two Macs? There seems to be only a single KVM switch that does that, and it's around $500. It also does not switch one Thunderbolt, but two Display Ports, so it seems that you would additionally need a bunch of adapters which split the USB-C Thunderbolt cable into two Display Port connections, and back together at the other end. Note that there seem to be more solutions for 4k, but it's my understanding that those don't work for 5k.

perryh2 5y ago
If you aren't switching between your computers too often, you can just get a USB hub like this and switch between display inputs from your monitor: https://www.amazon.com/gp/product/B083JKDNRJ/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 https://www.amazon.com/gp/product/B083JKDNRJ/ref=ppx_yo_dt_b...
- anyfoo 5y ago
  My monitor only has a single input, that's the problem I'm trying to solve. I don't need to switch USB.
ggayan 5y ago
Use a DP 1.4 switch: https://www.amazon.com/Angusplay-DisplayPort-Switch-Bidirectional-Splitter/dp/B089SLDDZZ/ref=sr_1_3?dchild=1&keywords=thunderbolt+switch&qid=1619119846&sr=8-3 https://www.amazon.com/Angusplay-DisplayPort-Switch-Bidirect... I tried ConnectPro's DP 1.4 KVM and the display blacked out constantly in MacOS. Friends who purchased the same KVM ran into the same issue with displays that push DP spec to the limit like 3440x1440@144. The switch I shared works just fine. From time to time (once every 1-2 months maybe) the display blacks out for a second but a computer restart does the trick, or reconnecting cables. Also make sure to get HBR3 displayport certified cables.
- anyfoo 5y ago
  Just to confirm, this does work with LG 5k monitors? The resolution there is 5120x2880, which is significantly more (the vertical resolution alone is doubled, and then some for the horizontal), but I don't know the refresh rate, so the bandwidth could still be similar maybe. EDIT: I'm also wondering, the only switch I know to be working uses two display port cables to the monitor (which I'd have to adapt to one Thunderbolt 3 instead), while your device only uses one. That doesn't bode well...

Camillo 5y ago

If you're buying a hub now, you don't want any of these things, you want Thunderbolt 4. I'd really like to see an equivalent article for it.

Dylan16807 5y ago

> DisplayPort 1.4 can deliver 4K 60Hz video using only two lanes, with a new high-bit-rate mode called HBR3 with a compression mode called DSC. This makes it possible to get 4K60 video and USB 3.1 ports in the same hub, but only if the computer, hub, and monitor all support DisplayPort 1.4 and HBR3. You don't need DSC to display 4K60 over two lanes, only to go above that or add HDR too. Also displayport 1.4 support doesn't guarantee DSC for some reason.

z9qjk 5y ago

I think the whole concept of usb c/tb3 is flawed, cables should be inside the computer not outside. I have a fairly simple setup: 2017 Macbook Pro with two TB3 ports, a Dell monitor, an external SSD, a TB2 soundcard and a wireless usb mouse, because a traditional mouse works better in VMs than a Magic Mouse. This setup worked perfectly with a 2015 13" MBP: the HDMI port supports the Dell monitor, I connected my soundcard to the dedicated TB2 port and I still had two USB3 ports for my mouse and the external ssd. Now comes the revolutionized & courageous setup with two TB3 ports: First of all I had to buy a USB3 dock. That's ok but still 50 euros down the toilet. Then an Apple issued TB2-TB3 adapter which was another 100 euros. But then I figured I can't connect these devices at once so I've had to buy an Apple Issued Digital AV Adapter for another 100 euros. We are already at 250 euros and the fun part just starts: If I connect my Dell monitor and my soundcard (even turned off) at the same time the monitor starts to flicker and the soundcard starts spitting out dirty electrostatic noise. Yes, a good old ground loop! So now I can't listen to music with my soundcard and have my monitor plugged in at the same time. I can't use my wireless mouse because the wireless dongle is too far from my USB3 dock. I can't use my external ssd reliably because every time I put my Macbook to sleep it disconnects in a way that i have to phisically reconnect it. Every fkn time. So I thought, gee I just have to shell out another 300 euros for a Caldigit TS3+ and all my problems will be solved, right? USB-C ecosystem: hold my beer The statical noise comes through the TS3+ as well plus it heats up my Macbook to a completely pathetic degree, so it throttles. Because it has to be thin too. TDP is just stat for nerds. SSD is still unreliable and the dock is still too far from my mouse to have a stable connection. In the end I spent 550 euros on completely useless environmental waste bullsh*t that shouldn't exist at all. I get what Apple and the whole industry had in mind with usb-c but it is flawed by design. It has to be reengineered from the ground up.

qihqi 5y ago
Hope you don't speak Spanish and can enjoy this one: https://www.youtube.com/watch?v=-I9n-cjl7zg https://www.youtube.com/watch?v=-I9n-cjl7zg

GekkePrutser 5y ago

Aha. Now I understand why my Lenovo USB-C dock doesn't do 4K@60 on my Mac. It's not thunderbolt capable. By the way, it does have an extra limitation on Mac. It only supports one external display. Apparently this is due to the Mac lacking support for Multi Stream Technology over DisplayPort (because it has Thunderbolt instead). Unfortunately Thunderbolt hubs are very expensive as the article also mentions. So I added a DisplayLink adapter for my third display (one 4K@60 directly connected to a USB-C port, the hub on the other with one HDMI out and the display link and lots of other USB stuff :) ) By the way DisplayLink support is pretty good now on Mac. Even for the new chipsets. I wouldn't call it nonexistent as the article does. It does have some limitations though, like Night Light not switching on.

JoBrad 5y ago
The M1 laptops don’t support more than 1 external display, either. Same laptop with Intel chip does, though.
rahimnathwani 5y ago
"Apparently this is due to the Mac lacking support for Multi Stream Technology over DisplayPort" AIUI it's not the Mac (hardware) that lacks this support, but the operating system (MacOS). Running Windows on the same hardware will allow you to use two monitors.

protoman3000 5y ago

Yeah, USB C is a mess and Thunderbolt 3 is obviously the superior 1-cable technology. Unfortunately, though, Thunderbolt 3 is a piece of sh*t, too [1] [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1766076 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1766076

steveBK123 5y ago

TB3/USBC is insane and a mess. Whoever decided to use the same connector is insane. I have varying cables with the same connector which do: - Power but not data - USB Data but no/low power - USB Data but only at USB2 speed (why?) - USB Data but only USB3 - TB3 - LOL don't forget USB-PD At least in the late 90s ecosystem of a dozen different connectors you could visually identify them. Now I have various special unicorn cables around the house which look the same, but only work for use case X or Y or Z. Examples are things like - I have one cable that can charge my camera over USB-C, and one cable that can transmit data between my camera & MacBook.. but neither does both. I suppose I could acquire a third cable to accomplish that.

xenadu02 5y ago
This is a feature, not a bug. The USB-IF is just a bunch of manufacturers getting together to agree on a standard. The vast majority of them are interested in one thing: lowering the BOM. Cheap, cheap, cheap! That's what matters. Making things super cheap means making lots of the spec optional so they can re-use existing chip designs, less expensive cables, etc. If they can make things easier for customers that's a nice bonus but ultimately it doesn't matter. The free market does not always optimize for what you think it should optimize for.
vetinari 5y ago
Have look at the USB-C pinout, it will be obvious then. (E.g.: https://www.allaboutcircuits.com/technical-articles/introduction-to-usb-type-c-which-pins-power-delivery-data-transfer/ https://www.allaboutcircuits.com/technical-articles/introduc...) Wrt USB2 vs USB3 - these have separate pins and wires. USB3 requires four extra wires, which must be of higher quality than those for USB2; their presence is the difference between 2 EUR and 10 EUR cable. TB3 is quite different cable; if it is over 0.5m, it will be an active one.

posobin 5y ago

Previous discussion of this post (2019, 171 comments): https://news.ycombinator.com/item?id=21532795 https://news.ycombinator.com/item?id=21532795 It has also been mentioned in 10 other HN comment threads. Found via https://ampie.app/url-context https://ampie.app/url-context.

adamparsons 5y ago

It blew my mind the other day when work gave us one of Apple's hdmi/usb/charge multiport adapters, that it could power 4k60 and a USB3 port without using thunderbolt under the hood. It was my understanding its either 4k60 with no usb, or 4k30 with usb. I'm assuming its using this newfangled HBR3 under the hood, or perhaps it actually is using thunderbolt secretly.

rahimnathwani 5y ago
If you're talking about the "USB-C Digital AV Multiport Adapter", the product page lists which Macbooks can do 4k60, and which can only do 1080p60/4k30. Those which can do 4k60 all support TB3, so I'm guessing it uses Thunderbolt to achieve this.