More knowledge acquired... I used simple dd to create a usb from debian- live-8.3.0-amd64-gnome-desktop.iso. This image has NO EFI structure or files at all, so it can only boot in legacy bios mode. When the asus bios has CSM enabled this live image boots perfectly.
I think the evidence is pointing to something wrong with the EFI content of the ubuntu iso. Even when it starts off with CSM being asked to boot the legacy content, the presence of the EFI stuff is confusing the bios later, probably when it is asked to boot the live linux kernel. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1557894 Title: Strange usb device format and failure to boot on UEFI system To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/usb-creator/+bug/1557894/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
