Slow boot when external USB SSD is connected (Asus Z790 Dark Hero)

[John_38]

- Asus Z790 Dark Hero
- Samsung Portable SSD T7 Shield 4TB

- Windows 11: Secure Boot, CSM disabled, TPM on

The SSD extends the boot time by 40-50 seconds.
Q-Code is „Ad“ (ready to boot event) when the screen stays black for 40-50 seconds after POST.

Q-Code is „Fb“ (i guess fast boot?) when Fast boot is enabled, also here 40-50 seconds.

There is no option to not initialize USB devices or partially. Maybe this is not possible because of Secure boot or this TPM system?

Or does it has to do with VMD that is enabled by default? Tough the option under VMD is VMD mapping/Unmapping is disabled.

I also tried to no success:
- disabling Legacy USB support and XHCI (makes overall no difference)

While POST the external SSD is always shown independent of the UEFI settings.

[Jiaszzz_ROG]

Hello @John_38 

Thank you for reaching out to us.
Could you clarify the current BIOS version, and have you tried clearing CMOS and disabling VMD to see if that improves boot times? If possible, kindly connect the external SSD after the system has already booted.
If the longer boot time only occurs when the external SSD is connected, we suggest checking whether the enclosure has any firmware or driver updates available and cross-testing with other USB Type-C ports.

Thank you.