The OpenBoot firmware determines the hardware configuration of a system or virtual machine, provides interactive debugging facilities, prepares memory, and initializes I/O devices by executing their device drivers. OpenBoot also boots the operating system from a storage device or a network if configured to boot.
OpenBoot can be used for other server administration tasks below the OS level. Some devices contain firmware written in the FCode language that enables additional commands which you can enter at the OpenBoot okprompt.
The OpenBoot firmware is based on the specification IEEE Standard 1275-1994 for Boot (Initialization Configuration) Firmware: Core Requirements and Practices.
OpenBoot operating characteristics are controlled by configuration variables that are stored in nonvolatile memory (NVRAM). You can change the configuration variable values to tailor operating characteristics to your environment.
For information about OpenBoot commands and variables, refer to the Oracle OpenBoot 4.x Administration Guide and IEEE Standard 1275-1994 for Boot (Initialization Configuration) Firmware: Core Requirements and Practices.