Intel Extensible Firmware Interface

Extensible Firmware Interface Specification

324 12/12/00 Version 1.02

The LangCodes variable contains an array of 3-character (8-bit ASCII characters)

ISO-639-2 language codes that the firmware can support. At initialization time the firmware

computes the supported languages and creates this data variable. Since the firmware creates this

value on each initialization, its contents are not stored in non-volatile memory. This value is

considered read-only.

The Lang variable contains the 3-character (8 bit ASCII characters) ISO-639-2 language code that

the machine has been configured for. This value may be changed to any value supported by

LangCodes; however, the change does not take effect until the next boot. If the language code is

set to an unsupported value, the firmware will choose a supported default at initialization and set

Lang to a supported value.

The Timeout variable contains a binary UINT16 that supplies the number of seconds that the

firmware will wait before initiating the original default boot selection. A value of 0 indicates that

the default boot selection is to be initiated immediately on boot. If the value is not present, or

contains the value of 0xFFFF then firmware will wait for user input before booting. This means the

default boot selection is not automatically started by the firmware.

The ConIn, ConOut, and ErrOut variables each contain an EFI_DEVICE_PATH descriptor

that defines the default device to use on boot. Changes to these values do not take effect until the

next boot. If the firmware can not resolve the device path, it is allowed to automatically replace the

value(s) as needed to provide a console for the system.

The ConInDev, ConOutDev, and ErrOutDev variables each contain an EFI_DEVICE_PATH

descriptor that defines all the possible default devices to use on boot. These variables are volatile,

and are set dynamically on every boot. ConIn, ConOut, and ErrOut are always proper subsets

of ConInDev, ConOutDev, and ErrOutDev.

Each Boot#### variable contains an EFI_LOAD_OPTION. Each Boot#### variable is the

name “Boot” appended with a unique four digit hexadecimal number. For example, Boot0001,

Boot0002, Boot0A02, etc.

The BootOrder variable contains an array of UINT16’s that make up an ordered list of the

Boot#### options. The first element in the array is the value for the first logical boot option, the

second element is the value for the second logical boot option, etc. The BootOrder order list is

used by the firmware’s boot manager as the default boot order.

The BootNext variable is a single UINT16 that defines the Boot#### option that is to be tried

first on the next boot. After the BootNext boot option is tried the normal BootOrder list is

used. To prevent loops, the boot manager deletes this variable before transferring control to the

pre-selected boot option.

The BootCurrent variable is a single UINT16 that defines the Boot#### option that was

selected on the current boot.

Each Driver#### variable contains an EFI_LOAD_OPTION. Each load option variable is

appended with a unique number, for example Driver0001, Driver0002, etc.

The DriverOrder variable contains an array of UINT16’s that make up an ordered list of the

Driver#### variable. The first element in the array is the value for the first logical driver load

option, the second element is the value for the second logical driver load option, etc. The