Skiboot (Skiboot): Late-stage boot firmware chainloaded by Hostboot after memory initialization. Performs wider platform initialization, including initialization of on-die PCI Express host bus controllers (PHBs). Also implements the OPAL runtime abstraction layer, which remains resident in memory and is called by the running operating system to invoke platform-specific functionality. Chainloads a Linux kernel and initramfs embedded in the mainboard's PNOR boot flash, usually Skiroot.
Skiboot is open source.