P3421W, USB Type-B with USB Type-C usage?

Question

Hi everyone! Just purchased this monitor and was wondering if anyone could help clarify the USB-B port that's connected via USB-A. I'm using a MacBook 16' connected via USB-C to this monitor. Firstly – does the USB-B port serve any purpose if I'm using USB-C to connect to my MacBook already? I've done a few tests and it seems that devices (keyboard, mouse, phone, etc.) plugged into my monitor's USB ports are all detected on my laptop without needing to plug in the USB-A cable to the USB-B port. My guess is that the USB-B port is only there on the monitor when you use HDMI / DP to connect to the monitor, and not USB-C. I do notice if I use too many power hungry devices, the USB-A ports on the monitor can struggle to charge everything – my laptop usually gives a warning saying that I need to disconnect the power hungry USB devices. Which leads me to my second question – does the USB-B port offer more power draw for the USB-A ports, if I connect it alongside the USB-C cable? I've just purchased a USB-A to USB-C adapter so I can plug the USB-B to USB-A cable to the other ports on my MacBook. The monitor itself charges the laptop at 65W even though the MacBook requires 96W, but it does the job most of the time, even if I'm pushing it a little. I'm wondering, if I have too many USB devices plugged into the monitor, would it be worth plugging in the USB-B to USB-A cable to my MacBook as well, just to offload some of the heavy lifting from the USB-C cable, or does it not make a difference? Sorry if that was all a bit confusing - I actually have no idea how to test any of this, and am hoping someone here might have a bit of experience / knowledge to explain to me. Thank you!

DELL-Cares · Answer

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DELL-Chris M · Answer

You are referring to the provided USB Type-B to USB Type-A upstream cable. You are correct. We can see in the online P3421W User's Guide that if connecting to the P3421W HDMI or DP, the user must then also connect the USB Type-B to USB Type-A upstream cable to "enable" the USB downstream ports.

The User's Guide does not mention PD (power delivery) for the upstream port. You should connect it and test and post the results.

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