Boot process

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The WiiU has two processors -- an ARM core (inside the Latte, known as Starbuck) and a PowerPC core (Espresso). The boot process starts on the ARM core, which eventually bootstraps the PPC.

The code components involved in the WiiU's boot process are, in order:

  • (ARM) boot0 - A mask ROM which loads boot1 and verifies its SHA-1 hash against that stored in its ancast header.
  • (ARM) boot1 - Lives in the first block of NAND and loads IOSU from the NAND filesystem. It verifies IOSU as an ancast image, similar to boot0.
  • (ARM) IOSU - IOSU is the operating system running on the ARM core. It loads Cafe OS into memory, then bootstraps the Espresso.
  • (PPC) Espresso Boot ROM - The Espresso Boot ROM verifies the SHA-1 hash of Cafe OS against the hash stored in the ancast header.
  • (PPC) Cafe OS - The Cafe OS is the operating system running on the PowerPC core.