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	Executed on	Loaded from	Function
OTPROM	SBE core (on CPU chip)	eFuses	very first instructions executed loads SBE firmware from SEEPROM into SBE core
Self-Boot Engine (SBE)	SBE core (on CPU chip)	SEEPROM	initialises CPU core loads Hostboot
Hostboot	CPU core	SPI Flash	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. SBE executes OTPROM, which loads SEEPROM firmware into SBE PIBMEM
2. SBE executes SEEPROM firmware, which loads Hostboot firmware into CPU core
3. CPU executes Hostboot, which loads Skiboot
4. Skiboot loads OCC, Petitboot
5. Petitboot loads the operating system
6. operating system talks to firmware through OPAL

See also

• OpenBMC
• OpenPOWER

External Links

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