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+Introduction to OpenPOWER Firmware
+==================================
+
+The ``op-build`` project constructs a host firmware image for OpenPOWER
+machines.
+
+Firmware Components
+-------------------
+
+Buildroot
+  We use http://buildroot.net/ as the build system for assembling a firmware
+  image. `op-build` is a "Buildroot overlay". We build a kernel and initramfs
+  using buildroot to run the Petitboot boot loader in.
+SBE
+  the Self Boot Engine is the first unit inside the POWER processor to start
+  executing. It's job is to set up a core and load Hostboot.
+Hostboot
+  Low level system boot firmware. It brings up CPU cores, the OCC, Memory
+  and hands control over to OPAL (skiboot)
+OCC
+  The On Chip Controller is responsible for thermal limits and frequency
+  management.
+OPAL
+  The OpenPOWER Abstraction Layer, provided by skiboot
+skiboot
+  skiboot implements OPAL (the OpenPOWER Abstraction Layer). Skiboot is
+  boot and runtime firmware and is responsible for bringing up PCI and
+  providing runtime abstractions to the running OS.
+Linux
+  Once skiboot has finished setting up the machine, it hands control over
+  to a Linux kernel. This kernel provides device drivers and userspace to
+  run the bootloader, Petitboot
+Petitboot
+  The bootloader. It is a normal user-space process running on Linux that
+  searches the system for disks and network devices that it can boot the
+  OS from.