UEFI Forum Releases UEFI 2.3.1 Specification Update
 

The UEFI Forum has ratified an update to the UEFI 2.3.1 Specification that adds important firmware considerations and addresses numerous engineering change requests. The updated Specification will be referred to as "UEFI 2.3.1C".

UEFI 2.3.1C adds: An OS Indications Variable - OS/FW feature & capability communication – when implemented, allows end-users to make an OS menu request to enter BIOS setup after next reboot.
UEFI 2.3.1C adds: A mechanism which, when implemented, facilitates Open Source Operating System installations and OS- agnostic end-user configurations of retaining the factory default keys while in Setup Mode (see Specification for full technical detail of Setup Mode).
UEFI 2.3.1C removes: Runtime driver requirement on Network UNDI drivers - this allows UNDI drivers to be delivered in EFI Byte Code (EBC) Virtual Machine format supporting systems based on different processor architectures.

http://www.techpowerup.com/168559/UE...on-Update.html