Classic Mac OS debugging output

You can make the Classic Mac OS dump a bunch of debugging output during boot.

Instructions

1. Boot into Open Firmware (Command-Option-O-F).
2. Since log output is massive, consider logging over the network instead of to the screen:
   1. Run dev /packages/telnet.
   2. Run " enet:telnet,192.168.18.10" io, substituting the IP address as necessary.
      • On-screen text input and output will end.
   3. On another computer, telnet into that IP address.
      • The screen will blank itself until booting begins.
3. Use the #Bitflags table to choose a debugging configuration.
4. Run dev / 3013FFF encode-int " AAPL,debug" property, substituting the hexadecimal number as necessary.
5. Run mac-boot.

Bitflags

From the beginning of the debugging output:

AAPL,debug bit settings (-OR- bits together):
       1 * = Print general informative messages.
       2 * = Print formatted Mac OS tables (except config/universal info).
       4 * = Print formatted config info table.
       8 * = Dump Mac OS tables (except config/universal info).
      10 * = Print node names while copying the device tree.
      20 * = Print property info while copying the device tree.
      40 * = Print interrupt-related info.
      80 * = Print interrupt tree traversal info.
     100 * = Print address resolution info.
     200 * = Print NV-RAM info.
     400 * = Print Mac OS "universal" info.
     800 * = Print "special" node info.
    1000 * = Load EtherPrintf utility via parcel for post FCode debugging.
    2000 * = Print BOOTP/DHCP/BSDP information.
    4000   = Allocate writable ROM aperture.
    8000   = Mark Toolbox image as non-cacheable.
   10000 * = Print parcel info while copying the device tree.
   20000   = Print information on device tree data checksums.
 1000000 * = Enable the Nanokernel debugger.
 2000000 * = Display the Nanokernel log during boot.
10000000   = Dont attempt to unhibernate system.
40000000   = Halt after end of FCode (useful if outputting to screen).

Adding all the bitflags together that enable logging (anything with an asterisk) gives 3013FFF.

Notes

• This does not work on a tray-loading iMac G3 because /packages/telnet does not exist.
• Telnet output starts about two seconds after the screen turns gray. Output then ends, before the Happy Mac even appears.
  • When this happens, the following is printed to the screen: Off to MacOS. The next (and last) call into OpenFirmware is quiesce().
• After telnet output ends, a separate NanoKernel Log will appear on screen, get covered by the Welcome to Mac OS dialog, then appear a second time before disappearing entirely with the "Starting up..." text.