Dell Latitude E7470 w/ Touchscreen External USB mouse and keyboard issues at Preboot
We have a few Dell Latitiude E7470 systems with touchscreen that have an issue in the pre-boot environment. Their USB mouse and keyboard will not function unless we disable secure boot and enable the Enable Legacy Option ROMs option. The attached mouse pad and keyboard work fine.
The Dell E7470 machines we have without the touchscreen are able to use an external USB mouse and keyboard just fine at preboot with Secure Boot enabled and Enable Legacy Option ROMs disabled. .