Not quite well-known issue, but still we want to share a tutorial on how to fix MT65xx preloader issue.

Solution for Unknown Device MT65xx preloader

In case you’re flashing your Xiaomi Redmi Note 4 device using SP Flash Tool (this guide also should help with other device models, not only Redmi Note 4, but that’s not for sure), you’ve installed all the required drivers, but your PC still can’t find your device successfully and in device manager it displayed as “Unknown device MT65xx preloader” then try following the steps below:

  1. First open USBDeview and delete all unknown devices (MT65xx preloader). Just in case you can also delete all other related and previously installed drivers, but this is optional. You can download USBDeview here
  2. Turn off your device and connect in to your PC via USB-cable.
  3. On the first 2-3 seconds after you’ve connected your phone to PC, in “Device Manager” select MT65xx preloader unknown device and manually install these drivers: SP_Drivers_v1.5.rar (MT65xx preloader drivers)

These steps could be done before pressing “Download” button in SP Flash Tool. If everything is fine then your device should be identified as “MediaTek PreLoader USB VCOM Port”, and then connect your device for flashing.