©ASUSTEK COMPUTER INC. ALL RIGHTS RESERVED.

andyxl987 · ‎05-09-2025

What is the issue?

Every time the monitor/computer connection is established, Windows notifies that an error with the USB connection has occurred (note: I do not and will notuse SmartKVM). This is annoying enough, but there is a biggerissue here that I think has so far gone unreported in these previous reports. The downstream connections via USB-C are atUSB 2.0 speed only. While many (if not most) devices will work in USB 2.0 speeds, they will be limited, e.g. my Logitech Brio is only capable of a 1080p30 recording under USB 2.0. The USB-B connection works fine.

This seems to be a common issue across this (and other ASUS monitors), e.g. see

I'm sure there are many more occurrences of this across these forums, essentially the issue is unfixed for more than one year with no response from ASUS.

What is the expected behaviour?

Windows does not notify about a USB error any time the hub is reconnected, e.g. during a KVM switch or restarting the computer. Devices should connect at USB 3.2 speeds, e.g. the Logitech Brio 4K Ultra HD camera should offer 4K30 and 1080p60 resolutions.

What is your configuration?

ASUS ROG Swift OLED PG34WCDM — firmware version: MCM106, Type-C Bandwidth: 3.2
ROG STRIX X870-I GAMING WIFI — USB-B connected desktop
ASUS ROG Zephyrus M16 (2022) GU603 — USB-C connected laptop
Windows 11 Pro 24H2 — all systems are up-to-date, I've also confirmed the USB speed issue in Ubuntu 22.04

This should be easy to reproduce, it's using all ASUS hardware.

Anything Else?

You can use USB Device Tree Viewer to confirm the differences between the device layout when using USB-B and USB-C. When using USB-C, any USB downstream devices connected will operate a maximum of 480 Mbps.

I don't know much about the USB spec but from what I could tell, there is a port on the Hub which corresponds to a 3.0 port (companion port) and it fails to initialize, this causes the Windows error. As for devices using only USB 2.0 speed, think the attached devices have already been connected at 2.0 speeds before this point anyway. Crucially, we see that with the USB-B connection there are 2 hubs, Realtek USB 3.2 Gen 1 USB Hub and Realtek USB 2.1 USB Hub. however, with the USB-C connection there is only the Realtek USB 2.1 USB Hub.

The monitor currently does not work as expected with non functional (when accessed from USB-C upstream) USB 3.2 ports, they are effectively USB 2.0 downstream ports in this configuration.

PG34WCDM - USB-C Bandwidth Limited to USB 2.0 Speed and Port Reset Failed Error