It has no UEFI which is weird since UEFI was already pretty standard at the time the Gen8 was designed. Plus it is very picky with booting from USB. First it doesn't want to boot from the blue USB 3.0 ports. Second it only boots from USB devices formatted with MBR and where its first partition is FAT32 formatted with sector sizes not bigger than 16kb (Source: a 'reputable source' in the HP Community).
But now comes the worst characteristic about the Gen8. You can't change the boot order of the SATA devices. So if you use the ODD power cable (with an ODD to SATA adapter of course) and the "SATA ODD" port, you have a journey to go as the boot order is as follows: The leftmost drive, followed by the next 3 drives - and finally the device connected tot eh SATA ODD port. There's also a "CDROM Drive" boot order item in the boot order menu - but it doesn't boot the SATA ODD port, only if there's a real CDROM drive.
The Gen8 has an internal USB port and