The Supermicro X9SRA mainboard (see http://www.supermicro.com/products/motherboard/Xeon/C600/X9SRA.cfm) has an AMI BIOS. There are at least two issues:
1) You can't disable the 'Intel ME' feature. There are problems with the 'mei_me' driver in Linux which freeze the system while booting up. The workaround is to disable 'Intel ME' which you can't do with this BIOS. Another workaround is to blacklist the 'mei_me' kernel module.
Blacklist via additional kernel parameter:
Blacklist in initrd (Debian / Ubuntu):
echo "blacklist mei_me" >>/etc/modprobe.d/blacklist.conf update-initramfs -k all -u
2) There is no documented hotkey for the interactive boot device selection screen. Not in the mainboard documentation and even not as a hint on the boot screen. :(
After trying different keys I found out that it's the F11 key.
You have to add the device categories (e.g. 'CD/DVD drive' or 'USB Hard Disk') as 2nd boot device in order to make them show up in the boot device selection screen.