OpenPOWER Firmware

OpenPOWER Firmware is an open-source alternative to OpenFirmware and proprietary IBM firmware used on Power machines. It is a general name for many separate pieces of software used to start recent Power Architecture chips made by IBM.

OpenBMC is a separate project that creates firmware for the Baseboard Management Controller.

Components

Firmware	Runtime Location	Function
Self-Boot Engine (SBE)	SBE core (on CPU chip)	initialises CPU core loads Hostboot
Hostboot	CPU core	loads Skiboot inits DRAM (zeroing for ECC mem.), Processor Bus, Memory buffer
Skiboot	CPU core	implements OpenPOWER Abstraction Layer (OPAL) for OS runtime services setup PCIe, device tree, real time clock, NVlink, sensors loads Petitboot, OCC
Petitboot	CPU core	boot menu loads operating system
On-Chip Controller (OCC)	OCC core (on CPU chip)	thermal regulation on CPU chip

Process

1. OpenBMC starts SBE
2. SBE loads Hostboot
3. Hostboot loads Skiboot
4. Skiboot loads OCC, Petitboot
5. Petitboot loads the operating system
6. operating system talks to firmware through OPAL

External Links

• OpenPOWER github account
• OpenPOWER firmware documentation
• OpenPower Firmware Stack - Joel's Weblog