Mini Is Not IOS -- but it is a limited replacement that can fulfill many low-level tasks that IOS might interfere with. The name is an allusion to GNU, which stands for "GNU's Not Unix"
- Light-weight -- binary is approximately 50kbytes, 11,673 lines of code as of first release
- Mostly IRQ driven :)
- Supports debug output over the GPIO pins and USBGecko
- Supports loading both ARM and PPC-side binaries over USBGecko (ala Wiiload)
- Allows any memory address to be peeked or poked from the PPC (via IPC)
- Contains drivers for the following hardware:
- Not dependent on IOS in any way -- as long as you can run it, it can do whatever it wants, regardless of what security features Nintendo patches into newer versions of IOS.
- No real kernel architecture; no threading model, but most calls are asynchronous
- No USB support (including Bluetooth for Wiimotes)
- No WiFi support
- No NAND FS support
- No audio/visual capability (hardware limitation)
All registers are exposed over IPC, so some or all of the missing driver functionality could conceivably be implemented on the PPC side. Note that this cannot execute at the same time as IOS; you can only have one or the other executing at any point in time. Switching back and forth between the two is left as an exercise for the developer.
Since the discovery of the AHBPROT register, Mini enables direct PPC access to all devices. It is often used together with Wii Linux to enable full hardware functionality and performance.
There is a PowerPC skeleton at: http://bootmii.dreamhosters.com/