...
- if x = 0 returns "ok\n"
- if x = 1 returns MMU2 firmware version
- if x = 2 returns MMU2 build number
- if x = 3 return power failures count
Mx
- if x = 0 sets mmu to normal mode
- if x = 1 sets mmu to stealth mode
...
- recover after eject
- currently just R0
Wx
- used in MMU load fail
- currently just W0