I recently got a 64GB USB stick and planned to make it a system repair multitool, with different Linux and Windows installers and live images, but I seem to have a USB stick that cannot be booted.
Pendrive Linux' Yumi installer doesn't recognize it, and only lists it when "show all devices" is checked.
The Windows 7 USB install tool doesn't recognize it either.
When putting an image on it with either Yumi or diskpart and xcopy, none of the three PCs I tested are able to boot it, but none of them have problems booting from another smaller, slower 8GB drive. The HP USB format tool, as mentioned in this answer does format it, but that does not enable bootability. I have tried both NTFS and FAT32 filesystems, but neither succeed.
What causes this? I was under the impression that USB sticks are just storage devices (like optical discs) and that it was enough to have the correct files/structures to make it bootable. Is the device missing some critical feature necessary to make it bootable?
The mainboards of the PCs are the GA-MA770T-UD3 (AM3 socket, probably a bit old), the GA-Q87TN (1150 socket), and whatever is inside the Dell XPS12 9Q33. The latter two run Haswell processors with UEFI, I can't imagine that a 64GB stick would pose a problem.
I also tried formatting with the Windows tools, and tried to make a partition of only 20GB.