[SOLVED] USB-C bandwidth & limitations ?

[ethan206]

I was looking into USB-C docks and was getting confused on their limitations (or more so my laptop's limitations). This Anker USB-C one (https://www.amazon.com/Anker-Docking-PowerExpand-Charging-Ethernet/dp/B088F7SY6S/ref=sr_1_3?crid=2MOTUM0IGEI36&keywords=anker+usb+c+dock&qid=1673423971&sprefix=anker+usb+c+dock,aps,134&sr=8-3&ufe=app_do:amzn1.fos.f5122f16-c3e8-4386-bf32-63e904010ad0) supports DP, HDMI, USB, PD, Ethernet, among other stuff as well. But plugging this into my laptop (which supports USB 3.1 10Gbps w/100W PD and DP 1.4) through a singular USB-C cable would be bottlenecked, wouldn't it? If I connect a 1440p 144Hz display, a 1Gbps Ethernet connection, along with an external NVMe SSD (10Gbps), plus all my peripherals, wouldn't some end be bottlenecked to an extent? Suppose on top of all of that, I also add another high-speed external drive (10Gbps) and a 4K display through HDMI, would I run into serious bottleneck issues with bandwidth limitations?

And on top of all of that, the hub would still be able to provide 85W for my laptop and supply power to all my connected devices? Would there be a way to disable the PD into my laptop as 85W isn't enough to power it (it requires 230W and I use a barrel plug)?

 

[hotaru.hino]

DisplayPort doesn't interact with the USB channel, so there's no bottleneck there. The bottleneck will simply be from the other peripherals because they'll be sharing a single USB link. But this is only a problem if you hammer all of those ports at once. So plugging in an external NVMe SSD isn't going to cut the Ethernet speed unless the SSD is doing something. And even then, the Ethernet port is likely going to have higher priority for link usage. Further reading: https://web.archive.org/web/2016122...ng_Kong_2016_-_DisplayPort_Alternate_Mode.pdf

Regarding charging, unless the USB-C port on the laptop is specifically marked as a charging port, it's not going to attempt to charge from the hub. Even then, there's a lot of handshaking involved between USB-PD devices and chargers to ensure that charging is even possible.

 

[ethan206]

DisplayPort doesn't interact with the USB channel, so there's no bottleneck there. The bottleneck will simply be from the other peripherals because they'll be sharing a single USB link. But this is only a problem if you hammer all of those ports at once. So plugging in an external NVMe SSD isn't going to cut the Ethernet speed unless the SSD is doing something. And even then, the Ethernet port is likely going to have higher priority for link usage. Further reading: https://web.archive.org/web/2016122...ng_Kong_2016_-_DisplayPort_Alternate_Mode.pdf

Regarding charging, unless the USB-C port on the laptop is specifically marked as a charging port, it's not going to attempt to charge from the hub. Even then, there's a lot of handshaking involved between USB-PD devices and chargers to ensure that charging is even possible.

Ah, I see. In that case, would plugging the external drive into another USB-C port on my laptop solve the bandwidth issue (if I run into it)? Or is that 10Gbps link shared across all ports? Here's my laptop's USB specifications (Blade 14 2021):

https://imgur.com/a/x7SlOPQ

View: https://imgur.com/a/x7SlOPQ


And if DP is using it's own separate channel, I would assume HDMI is also the same too? So if I plug in a 4K display through HDMI on that hub, that shouldn't be bottlenecked either correct?

 

[LordVile]

DisplayPort doesn't interact with the USB channel, so there's no bottleneck there. The bottleneck will simply be from the other peripherals because they'll be sharing a single USB link. But this is only a problem if you hammer all of those ports at once. So plugging in an external NVMe SSD isn't going to cut the Ethernet speed unless the SSD is doing something. And even then, the Ethernet port is likely going to have higher priority for link usage. Further reading: https://web.archive.org/web/2016122...ng_Kong_2016_-_DisplayPort_Alternate_Mode.pdf

Regarding charging, unless the USB-C port on the laptop is specifically marked as a charging port, it's not going to attempt to charge from the hub. Even then, there's a lot of handshaking involved between USB-PD devices and chargers to ensure that charging is even possible.

Not so fast there, DP is an optional extra on usb 3.1 and the device has to support it. Also cables aren’t magic you will run into speed bottlenecks if you’re trying to push a 10Gbps signal and DP through the cable. It’s not Thunderbolt

 

[Karadjgne]

If you have seperate usb-c ports on your laptop, they'll be seperate circuits going through a super i/o, no different to a desktop pc. They won't be daisy-chained in a single internal circuit.

A single usb-c still uses a super i/o, which distributes the signaling to the appropriate resources, be that video chipsets, sound chipsets, storage or cpu etc.

But that single port is a McDonald's straw, it has limitations, even though the largest straw available. You aren't going to fill the bathtub with it, in any kind of hurry.

 

[hotaru.hino]

Ah, I see. In that case, would plugging the external drive into another USB-C port on my laptop solve the bandwidth issue (if I run into it)? Or is that 10Gbps link shared across all ports? Here's my laptop's USB specifications (Blade 14 2021):

And if DP is using it's own separate channel, I would assume HDMI is also the same too? So if I plug in a 4K display through HDMI on that hub, that shouldn't be bottlenecked either correct?

Plugging the drive into another port won't cause a bottleneck for the dongle for the other devices connected to it.

If the dongle has HDMI, it likely is converting DP into HDMI.

Not so fast there, DP is an optional extra on usb 3.1 and the device has to support it. Also cables aren’t magic you will run into speed bottlenecks if you’re trying to push a 10Gbps signal and DP through the cable. It’s not Thunderbolt

Their device does support it.

And USB-C pins can be configured to support DP and USB 3.x at the same time. It was in the presentation I linked:

If you're asking how:

USB 3.x only needs one of the TX+/- and RX +/- pairs. DP monitors don't transmit anything, so the RX +/- of the other pair becomes a TX+/-, and thus gives you two lanes of DP.

 

[ethan206]

Plugging the drive into another port won't cause a bottleneck for the dongle for the other devices connected to it.

If the dongle has HDMI, it likely is converting DP into HDMI.


Their device does support it.

And USB-C pins can be configured to support DP and USB 3.x at the same time. It was in the presentation I linked:

If you're asking how:

USB 3.x only needs one of the TX+/- and RX +/- pairs. DP monitors don't transmit anything, so the RX +/- of the other pair becomes a TX+/-, and thus gives you two lanes of DP.

Oh, is there a way for the dongle to pass through DP (like without converting it to HDMI)? I'm using G-SYNC and G-SYNC isn't compatible with HDMI (as far as I'm aware) or will that not be a issue?

So from what I'm gathering from all of this is that I shouldn't run into a speed bottleneck despite not having Thunderbolt? And in that scenario, I would be connecting a DP 1.4 display (32.4Gbps bandwidth through DP lanes on USB-C), a high-speed NVme external drive (10Gbps bandwidth on shared USB-C, TX), a 1GBps Ethernet connection (which is shared with the 10Gbps USB-C TX, but Ethernet is given priority). And all my other peripherals (mouse, keyboard, microphone) connected as well (which I assume would not be a huge issue for bandwidth?).

 

[hotaru.hino]

Oh, is there a way for the dongle to pass through DP (like without converting it to HDMI)? I'm using G-SYNC and G-SYNC isn't compatible with HDMI (as far as I'm aware) or will that not be a issue?

Unless one of the ports of the dongle outputs DP, no. Which specific dongle do you have?

So from what I'm gathering from all of this is that I shouldn't run into a speed bottleneck despite not having Thunderbolt? And in that scenario, I would be connecting a DP 1.4 display (32.4Gbps bandwidth through DP lanes on USB-C), a high-speed NVme external drive (10Gbps bandwidth on shared USB-C, TX), a 1GBps Ethernet connection (which is shared with the 10Gbps USB-C TX, but Ethernet is given priority). And all my other peripherals (mouse, keyboard, microphone) connected as well (which I assume would not be a huge issue for bandwidth?).

Unless you're transferring a massive file from the external SSD to an internal NVMe one or RAM (such as program data loading), no. And I'm speculating that Ethernet has priority since network traffic often requires time sensitive responses, but I don't actually know. Same with the other peripherals.

 

[ethan206]

Unless one of the ports of the dongle outputs DP, no. Which specific dongle do you have?


Unless you're transferring a massive file from the external SSD to an internal NVMe one or RAM (such as program data loading), no. And I'm speculating that Ethernet has priority since network traffic often requires time sensitive responses, but I don't actually know. Same with the other peripherals.

I'm using the Anker Dock linked in the original post but I think it does just transfer DP into HDMI. Thanks for your help!