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Does anybody know why there are no USB-C hubs? With USB-A there are hubs that have four or eight USB-A outputs. But with USB-C I can’t find any hubs that have f

Does anybody know why there are no USB-C hubs? With USB-A there are hubs that have four or eight USB-A outputs. But with USB-C I can’t find any hubs that have four USB-C outputs. Some have four USB-A but none have four USB-C output. Pretty strange and quite a loss of functionality.

shantly 7y ago
Guesses: 1) not that many people have four USB-C devices they need to plug in at once (unlike USB-A), 2) it'd probably be super expensive and in some cases impossible to support all the abilities of USB-C across 4 ports, leaving only some small subset of capabilities available on all four and maybe forcing you to not use some of the ports at all if one or two of them have higher-end capabilities and you're actually using them for that. Experience is probably confusing and frustrating at best—and expensive anyway.
EwanToo 7y ago
I've seen statements (that I can't verify) that chip support doesn't exist yet for additional usb-c ports. I guess negotiating the bandwidth and power delivery would be pretty complex
zifutreiua 7y ago
Maybe there is no market for them yet? Besides phones and laptops there are not many USB-C devices out there yet. And you don't connect phones and laptops to hubs (as a guest, not a host).
- greggman2 7y ago
  > Maybe there is no market for them yet? Then I guess the title "USB-C Has Finally Come into Its Own" is a lie.
- pfranz 7y ago
  Sony's pretty popular BT headphones, WH1000XM3, switched to USB-C about a year ago. I've noticed a bunch of external hard drives have, too. I picked up a micro-b to USB-C cable so I wouldn't need an adapter. Nintendo Switch was released in early 2017. It's difficult to even find chargers with more than 1 USB-C port. Apple has been shipping laptops with only USB-C since 2015. Many people rely heavily on dongles and breakout boxes. A USB-C hub would be welcome even at a steep premium. My guess is that all of the tech that tunnels through USB-C would be really difficult to hub or to share. Which is why the closest thing I've seen to a hub is a passthrough plus a USB-C for power.
cerberusss 7y ago
Apple sold them for a certain period, made by Belkin. https://www.amazon.com/Belkin-Linksys-B2B153-04-BLK-4-Port-Desktop/dp/B07932P4GM https://www.amazon.com/Belkin-Linksys-B2B153-04-BLK-4-Port-D...
- nespressoAnger 7y ago
  Technically, yes. But I would point out that the linked device has 1 USB-C Power Delivery pass-through, 1 USB-C data port, and 2 USB-A ports. Nobody has yet shipped a USB hub with more than 1 USB-C downstream data port.
  - cerberusss 7y ago
    I linked the wrong one. I'm very sure that with the introduction of the (USB-C only) MacBook Pro, they sold a hub with an upstream USB-C port, and four downstream USB-C ports. After some time, it wasn't available anymore. It was bus-powered, so I'm pretty sure it was simply a bunch of USB-C ports that offered no more than USB 3.0 and that didn't support USB-PD. Can't seem to find it anymore.
  - cerberusss 7y ago
    Found one; https://www.sitecom.com/en/usb-c-hub-4-port/cn-386/p/1881 https://www.sitecom.com/en/usb-c-hub-4-port/cn-386/p/1881
xenadu02 7y ago
Supporting the alternate modes, Thunderbolt 3, power delivery, etc with a hub isn't trivial. Thunderbolt requires a PCI bridge for starters. It is highly likely any such hub would be a USB-3.x hub only but wouldn't support power pass-through properly, you wouldn't be able to connect your monitor to it, etc.
nespressoAnger 7y ago
Because, unlike USB-A hubs, it's not clear what should happen when you plug in a new device. This is mostly due to the existence of alternate modes. For example, let's say you have a USB-C hub with 4 downstream ports and two USB devices plugged in. At least one of these is a 10Gbps USB 3.1 device. You plug in a USB-C -> HDMI adapter. Which of the following happens (and how does your grandmother diagnose the problem)? 1. Nothing. 2. The three existing devices detach from the bus and re-enumerate as USB 2.0 at 0.480 Gbps 3. The three existing devices continue to run as 3.0 devices, but only at 5 Gbps 4. The three existing devices continue to run as 3.0 devices at 10 Gbps Explanation: 1. The hub does not support USB alt modes, so when an HDMI dongle is plugged in, the dongle is ignored. 2. The HDMI dongle is a passive alt mode device, requiring the use of all 4 high speed lanes. The other downstream devices are routed the internal USB 2.0 hub. 3. The HDMI dongle has an active Displayport -> HDMI converter inside, and uses only 2 of the high speed lanes, leaving the other 2 for USB 3.0 data. Since the other peripherals use the 2x 5Gbps USB 3.1 mode and only 1 lane is available in each direction, they revert to 5Gbps 4. Same as #3, except that the peripherals use the 1x 10Gbps USB 3.1 mode, so they continue to operate at 10Gbps with a single lane. Ok, now 3 ports are occupied and you plug in a pair of USB-C headphones. What happens now? 1. Nothing 2. Your HDMI dongle stops working 3. Everything Just Works Explanation 1. USB alt modes don't cover the case of a USB Audio Accessory and a Displayport accessory. Since you can't have both, your drivers ignore the new device 2. Same as #1, but your drivers prioritize the new device 3. Maybe your hub secretly has an audio codec inside, and is able to sync and source analog audio to any downstream port. Bonus points: Ok, now what happens when you chain USB-C hubs? What happens when you try to plug in multiple HDMI adapters? Multiple audio accessories? When things don't work, is the problem the hub, the peripheral, or the drivers?
- Ididntdothis 7y ago
  Thanks! This seems a major shortcoming with USB-C if you want to build docking stations. And it will get worse once everything uses USB-C. I have already converted my USB drives back to USB-A so I can use them with one hub that’s plugged into my laptop.
- cesarb 7y ago
  From what I've read of the official specification, the correct answers are: 1. Plug the HDMI adapter: almost nothing. The HDMI adapter enumerates as an USB 2.0 "billboard device". The operating system can read the descriptor from this device and present a pop-up explaining "you have to plug HDMI adapters directly". This is because, as far as I know, USB hubs can't pass through alternate modes (except for the new USB4 alternate mode, but that is less of "pass through" and more "the hub is a USB4 device itself"). 2. Plug the USB-C headphones: it depends on whether they are analog headphones using the "audio accessory" mode, or digital headphones presenting as an USB audio device. If they are digital headphones, it's the "everything just works" case; if they are analog headphones, it's the "nothing" case (unless there's something in the specification I missed where a hub can detect the "audio accessory" and warn the host, in which case you might get the pop-up explaining "analog headphones are not supported by this computer, even if you had plugged them directly"). Things change a bit with USB4. In the particular case where the HDMI dongle is an active DP to HDMI converter (which is probably the most common case, since from what I've seen computer support for the DP alternate mode is more common than the HDMI alternate mode, so most dongles will cater to that case), and the hub is an USB4 hub, it'll work as if it had been connected directly, since USB4 can tunnel Displayport (together with PCI Express and USB 3).
cerberusss 7y ago
Found one! Not sure of which countries this brand is sold, though. https://www.sitecom.com/en/usb-c-hub-4-port/cn-386/p/1881 https://www.sitecom.com/en/usb-c-hub-4-port/cn-386/p/1881

shantly 7y ago

Guesses: 1) not that many people have four USB-C devices they need to plug in at once (unlike USB-A), 2) it'd probably be super expensive and in some cases impossible to support all the abilities of USB-C across 4 ports, leaving only some small subset of capabilities available on all four and maybe forcing you to not use some of the ports at all if one or two of them have higher-end capabilities and you're actually using them for that. Experience is probably confusing and frustrating at best—and expensive anyway.

EwanToo 7y ago

I've seen statements (that I can't verify) that chip support doesn't exist yet for additional usb-c ports. I guess negotiating the bandwidth and power delivery would be pretty complex

zifutreiua 7y ago

Maybe there is no market for them yet? Besides phones and laptops there are not many USB-C devices out there yet. And you don't connect phones and laptops to hubs (as a guest, not a host).

greggman2 7y ago
> Maybe there is no market for them yet? Then I guess the title "USB-C Has Finally Come into Its Own" is a lie.
pfranz 7y ago
Sony's pretty popular BT headphones, WH1000XM3, switched to USB-C about a year ago. I've noticed a bunch of external hard drives have, too. I picked up a micro-b to USB-C cable so I wouldn't need an adapter. Nintendo Switch was released in early 2017. It's difficult to even find chargers with more than 1 USB-C port. Apple has been shipping laptops with only USB-C since 2015. Many people rely heavily on dongles and breakout boxes. A USB-C hub would be welcome even at a steep premium. My guess is that all of the tech that tunnels through USB-C would be really difficult to hub or to share. Which is why the closest thing I've seen to a hub is a passthrough plus a USB-C for power.

cerberusss 7y ago

Apple sold them for a certain period, made by Belkin. https://www.amazon.com/Belkin-Linksys-B2B153-04-BLK-4-Port-Desktop/dp/B07932P4GM https://www.amazon.com/Belkin-Linksys-B2B153-04-BLK-4-Port-D...

nespressoAnger 7y ago
Technically, yes. But I would point out that the linked device has 1 USB-C Power Delivery pass-through, 1 USB-C data port, and 2 USB-A ports. Nobody has yet shipped a USB hub with more than 1 USB-C downstream data port.
- cerberusss 7y ago
  I linked the wrong one. I'm very sure that with the introduction of the (USB-C only) MacBook Pro, they sold a hub with an upstream USB-C port, and four downstream USB-C ports. After some time, it wasn't available anymore. It was bus-powered, so I'm pretty sure it was simply a bunch of USB-C ports that offered no more than USB 3.0 and that didn't support USB-PD. Can't seem to find it anymore.
- cerberusss 7y ago
  Found one; https://www.sitecom.com/en/usb-c-hub-4-port/cn-386/p/1881 https://www.sitecom.com/en/usb-c-hub-4-port/cn-386/p/1881

xenadu02 7y ago

Supporting the alternate modes, Thunderbolt 3, power delivery, etc with a hub isn't trivial. Thunderbolt requires a PCI bridge for starters. It is highly likely any such hub would be a USB-3.x hub only but wouldn't support power pass-through properly, you wouldn't be able to connect your monitor to it, etc.

nespressoAnger 7y ago

Because, unlike USB-A hubs, it's not clear what should happen when you plug in a new device. This is mostly due to the existence of alternate modes. For example, let's say you have a USB-C hub with 4 downstream ports and two USB devices plugged in. At least one of these is a 10Gbps USB 3.1 device. You plug in a USB-C -> HDMI adapter. Which of the following happens (and how does your grandmother diagnose the problem)? 1. Nothing. 2. The three existing devices detach from the bus and re-enumerate as USB 2.0 at 0.480 Gbps 3. The three existing devices continue to run as 3.0 devices, but only at 5 Gbps 4. The three existing devices continue to run as 3.0 devices at 10 Gbps Explanation: 1. The hub does not support USB alt modes, so when an HDMI dongle is plugged in, the dongle is ignored. 2. The HDMI dongle is a passive alt mode device, requiring the use of all 4 high speed lanes. The other downstream devices are routed the internal USB 2.0 hub. 3. The HDMI dongle has an active Displayport -> HDMI converter inside, and uses only 2 of the high speed lanes, leaving the other 2 for USB 3.0 data. Since the other peripherals use the 2x 5Gbps USB 3.1 mode and only 1 lane is available in each direction, they revert to 5Gbps 4. Same as #3, except that the peripherals use the 1x 10Gbps USB 3.1 mode, so they continue to operate at 10Gbps with a single lane. Ok, now 3 ports are occupied and you plug in a pair of USB-C headphones. What happens now? 1. Nothing 2. Your HDMI dongle stops working 3. Everything Just Works Explanation 1. USB alt modes don't cover the case of a USB Audio Accessory and a Displayport accessory. Since you can't have both, your drivers ignore the new device 2. Same as #1, but your drivers prioritize the new device 3. Maybe your hub secretly has an audio codec inside, and is able to sync and source analog audio to any downstream port. Bonus points: Ok, now what happens when you chain USB-C hubs? What happens when you try to plug in multiple HDMI adapters? Multiple audio accessories? When things don't work, is the problem the hub, the peripheral, or the drivers?

Ididntdothis 7y ago
Thanks! This seems a major shortcoming with USB-C if you want to build docking stations. And it will get worse once everything uses USB-C. I have already converted my USB drives back to USB-A so I can use them with one hub that’s plugged into my laptop.
cesarb 7y ago
From what I've read of the official specification, the correct answers are: 1. Plug the HDMI adapter: almost nothing. The HDMI adapter enumerates as an USB 2.0 "billboard device". The operating system can read the descriptor from this device and present a pop-up explaining "you have to plug HDMI adapters directly". This is because, as far as I know, USB hubs can't pass through alternate modes (except for the new USB4 alternate mode, but that is less of "pass through" and more "the hub is a USB4 device itself"). 2. Plug the USB-C headphones: it depends on whether they are analog headphones using the "audio accessory" mode, or digital headphones presenting as an USB audio device. If they are digital headphones, it's the "everything just works" case; if they are analog headphones, it's the "nothing" case (unless there's something in the specification I missed where a hub can detect the "audio accessory" and warn the host, in which case you might get the pop-up explaining "analog headphones are not supported by this computer, even if you had plugged them directly"). Things change a bit with USB4. In the particular case where the HDMI dongle is an active DP to HDMI converter (which is probably the most common case, since from what I've seen computer support for the DP alternate mode is more common than the HDMI alternate mode, so most dongles will cater to that case), and the hub is an USB4 hub, it'll work as if it had been connected directly, since USB4 can tunnel Displayport (together with PCI Express and USB 3).

cerberusss 7y ago

Found one! Not sure of which countries this brand is sold, though. https://www.sitecom.com/en/usb-c-hub-4-port/cn-386/p/1881 https://www.sitecom.com/en/usb-c-hub-4-port/cn-386/p/1881