iMac 5k 2014: USB Device disables Keyboard on Boot

[Alwis]

Hi,

for expanding my iMac storage I bought a Crusial X10 external SSD. The SSD was detected by the Mac, I formatted it and could write data to it.

But when rebooting the Mac I strange problem occurred: The Mac rebooted and showed the "Unlook drive" screen (I have Filevault activated). But in this screen I could use neither my wired Apple keyboard not my bluetooth mouse. Otherwise the Mac worked fine, after some time it showed a information regarding forgotten password, so it was not crashed.

I tried a different cable and also a Sandisk USB 3 USB drive, always the same result, even when plugging in the USB drive in one of the USB ports of my keyboard. When using a USB 2 drive I could use the keyboard again.

I have a Seagate Fast SSD, which is about 5 years old and works without any problems with this Mac.

I assume, that modern USB versions somehow cause problems with the USB controller and that Bluetooth is not working because it is connected via USB too?

Any ideas what is happening and what I could do about it?

Alwis

 

[Bigwaff]

What version of Mac OS is your iMac running?

 

[Alwis]

What version of Mac OS is your iMac running?

Big Sur, this was in preparation for installing Sonoma using OCLP.