Rairii wanted to know whether classic Mac OS could run on a Wii. He didn't need any more reason than that. The result: Mac OS 7.6 and 9.2.2 booting on a console that was never meant for office work.

The motivation is almost incidental. He had previously ported Windows NT to PowerPC Macs, became familiar with classic Mac OS that way, and found its "jank" fascinating. When he realised that the GameCube, Wii and Wii U all have chipsets from the same design team (ArtX, later absorbed into ATI), the question followed naturally.

What's in between

Classic Mac OS starts via a bootloader called "Trampoline", and that expects an Open Firmware environment. So first an OpenBIOS port had to be made, started on 22 June 2025.

Then followed a series of patches all with the same pattern: the software assumes something, and the console doesn't do that.

  • Physical addresses from 0x8000_0000 are treated as MMIO. On the Wii that isn't MMIO.
  • The Trampoline counts on a microcontroller that's in every PowerPC Mac and is missing here.
  • A function that initialises the ADB and power management doesn't check whether the hardware is there and overwrites a chunk of low memory.
  • A copy error in the serial port initialisation causes an infinite loop when port 2 is missing.
  • Without a USB controller, the USB keyboard driver crashes on a NULL pointer.

Each of those points is a few lines of patch. Together they're dozens, and the order matters.

What it costs

Mac OS 9.2.2 at first wouldn't get past startup. Cause: Open Transport, which can't handle a system without serial or network devices. Take the extension out, and it worked.

On real hardware, 7.6 started in about forty seconds, via SD over SPI, the slowest way there is.

The port hasn't been released yet. Next steps: the Wii's SD controller, USB, and then the Wii U.

Perhaps the most striking detail is in the introduction: no coding agent or LLM was involved. All the reverse-engineering, patching and debugging is manual work, done by someone who wanted to understand it.

Source: My favourite PowerMac is a Nintendo Wii — Rairii, Virtually Fun.