OpenPOWER Firmware

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OpenPOWER Firmware is an open-source alternative to OpenFirmware and proprietary IBM firmware used on Power machines.[1] It is a general name for many separate pieces of software used to start recent Power Architecture chips made by IBM.[2]

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


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


  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


See also

External Links