3 ms·

So you want to get 4 × 10W out of a single 2.5W (at most 10W) upstream port?

jedberg 4y ago
From what I've read the MacBook can output 15W on a port, so I'd expect a hub to be able to output 15W when one device is plugged in, 10W+5W with two, etc.
- vxNsr 4y ago
  The macbook is using thunderbolt, not pure usb-c.
  - jedberg 4y ago
    This is also a good point. Even I use the terms interchangeably when I shouldn't, and I should know better.
  - Snc 4y ago
    Note that these terms are not strictly comparable. USB-C is just a connector specification. There are many protocols that utilize USB-C: USB 3.2, USB4 and Thunderbolt being some of them.
- sebk 4y ago
  Not having ports with constant capabilities is a source of customer dissatisfaction when devices work when plugged in independently but not together. Consider for instance the new 14" and 16" MacBook pros: They got rid of the 4th Thunderbolt port in favor of an HDMI port, likely because of internal bandwith constraints. They could have kept Thunderbolt and HDMI, and only have one Thunderbolt port on the right side work when HDMI is plugged in, but they didn't, because having your external drive work only when your monitor is unplugged is unintuitive.
  - Gigachad 4y ago
    They were right originally when then went usb-c only. You could output hdmi on any port or do anything else with the port. We had gotten to the point where most offices had a usb-c adapter on the end of every loose hdmi cable so it wasn't an issue.
    - Bud 4y ago
      You mean Thunderbolt only. Not USB-C. Let's credit Apple for what they actually did, which was to go with the non-shitty port from the beginning even though it was expensive and everyone mocked them for doing so.
- eigen 4y ago
  doesnt §4.6 of the USB-C spec show the precedence of power source usage? I.E. there is no 10W option, just 3A, 1.5A, 0.9A, 0.5A at 5V or 15W, 7.5W, 4.5W, or 2.5W. so then your 15W port turns into 2x 7.5W ports or 3x 5W ports. I dont know if you can count on the upstream port being 15W. if its 7.5W do you do 4.5+2.5W and 3x 2.5W? also, I've found that no one obeys the current limit for inrush so now your downstream ports have to allow 7.5+W until they enumerate and you can lower the current limit. additionally, people are complaining about not being able to tell cables apart. can they tell the power requirements and calculate how much power a combination of devices requires?
  - Dylan16807 4y ago
    Those are only for dumb power supplies using resistors to signal max amount. Negotiated power is very granular. > additionally, people are complaining about not being able to tell cables apart. can they tell the power requirements and calculate how much power a combination of devices requires? If they don't know device power levels they can just learn what can simultaneously go on a single port when they try, like with USB 2.
Dylan16807 4y ago
At most 10W?
- kuschku 4y ago
  2A at 5V is the maximum you can get without USB-PD. 500mA 5V is the maximum that’s guaranteed.
  - Dylan16807 4y ago
    Why are we assuming no PD?

From what I've read the MacBook can output 15W on a port, so I'd expect a hub to be able to output 15W when one device is plugged in, 10W+5W with two, etc.

vxNsr 4y ago
The macbook is using thunderbolt, not pure usb-c.
- jedberg 4y ago
  This is also a good point. Even I use the terms interchangeably when I shouldn't, and I should know better.
- Snc 4y ago
  Note that these terms are not strictly comparable. USB-C is just a connector specification. There are many protocols that utilize USB-C: USB 3.2, USB4 and Thunderbolt being some of them.
sebk 4y ago
Not having ports with constant capabilities is a source of customer dissatisfaction when devices work when plugged in independently but not together. Consider for instance the new 14" and 16" MacBook pros: They got rid of the 4th Thunderbolt port in favor of an HDMI port, likely because of internal bandwith constraints. They could have kept Thunderbolt and HDMI, and only have one Thunderbolt port on the right side work when HDMI is plugged in, but they didn't, because having your external drive work only when your monitor is unplugged is unintuitive.
- Gigachad 4y ago
  They were right originally when then went usb-c only. You could output hdmi on any port or do anything else with the port. We had gotten to the point where most offices had a usb-c adapter on the end of every loose hdmi cable so it wasn't an issue.
  - Bud 4y ago
    You mean Thunderbolt only. Not USB-C. Let's credit Apple for what they actually did, which was to go with the non-shitty port from the beginning even though it was expensive and everyone mocked them for doing so.
eigen 4y ago
doesnt §4.6 of the USB-C spec show the precedence of power source usage? I.E. there is no 10W option, just 3A, 1.5A, 0.9A, 0.5A at 5V or 15W, 7.5W, 4.5W, or 2.5W. so then your 15W port turns into 2x 7.5W ports or 3x 5W ports. I dont know if you can count on the upstream port being 15W. if its 7.5W do you do 4.5+2.5W and 3x 2.5W? also, I've found that no one obeys the current limit for inrush so now your downstream ports have to allow 7.5+W until they enumerate and you can lower the current limit. additionally, people are complaining about not being able to tell cables apart. can they tell the power requirements and calculate how much power a combination of devices requires?
- Dylan16807 4y ago
  Those are only for dumb power supplies using resistors to signal max amount. Negotiated power is very granular. > additionally, people are complaining about not being able to tell cables apart. can they tell the power requirements and calculate how much power a combination of devices requires? If they don't know device power levels they can just learn what can simultaneously go on a single port when they try, like with USB 2.

Dylan16807 4y ago

At most 10W?

kuschku 4y ago
2A at 5V is the maximum you can get without USB-PD. 500mA 5V is the maximum that’s guaranteed.
- Dylan16807 4y ago
  Why are we assuming no PD?