Model & Firmware:
- Laptop: ASUS ROG Zephyrus G16 2025 (Model 5060, Ryzen AI 7 350)
- BIOS: v305 (issue also present when updated from v300 → v302 → v305)
- OS: Windows 11 Home, 10.0.26100 Build 26100
- External Monitor: HP Z27k G3, USB-C DisplayPort Alt Mode
- Cable: OEM HP USB-C to USB-C (verified working on other laptops)
Issue Summary
USB-C DisplayPort Alt Mode works only under very specific conditions and fails to re-initialize after the USB-C cable is unplugged.
The only temporary workaround is to re-flash the BIOS while the monitor is connected.
Steps to Reproduce
- Boot laptop with USB-C monitor attached → external display doesn't work.
- Disconnect the USB-C display cable.
- Re-connect the cable → monitor is not detected (no signal, no DP-Alt-Mode in Windows).
- Enter BIOS (F2 on boot) → Advanced (F7) → EZ Flash → re-flash the same BIOS v305 while the USB-C monitor is connected.
- After reboot, external display works again—until the cable is unplugged.
Additional Observations
- Tested on two brand-new units with identical results → hardware defect is unlikely.
- Windows driver re-installs, factory reset, and power-drain cycles do not resolve the issue.
- Other USB-C functions (charging, data, peripherals) work normally.
- If the monitor remains plugged in across restarts, it continues to function.
- Once the USB-C cable is unplugged—even while the laptop is off—video output will not return unless BIOS is re-flashed with the monitor connected.
Likely Cause
The USB-C controller / EC firmware appears not to re-initialize DP-Alt Mode after a cable hot-plug.
Re-flashing the BIOS seems to force a fresh initialization.
Request
Could ASUS engineering please investigate and provide a BIOS/EC firmware update to ensure proper USB-C DP-Alt Mode re-negotiation on hot-plug?
More details here: https://www.reddit.com/r/ZephyrusG14/comments/1lbpbu1/comment/ngqn5od/?context=3&utm_source=share&ut...
