Chameleon boot option arch=i386 is normally sufficient. Once booted up, use Terminal command uname -a to verify kernel mode. You'll see it immediately: i386 for 32bit and x86_64 for 64bit.
However, there's a flag -force64 to run apps in 64bit mode (it's required for some apps such as HWMonitor or PlistEditPro for instance). This flag aplies to user space. Check that out in your o.c.B.plist. You can use Chameleon Wizard too. OS X does support mixing 32bit kernel and 64bit apps; and vice-versa. You can Google for this. If the flag is present, remove it and apps will be liited to 32bit mode only (and an app such as PlistEditPro will no longer run).
I'm fairly certain that I've never specified this flag unless is implied - I tried adding '-force32' in o.c.B.plist kernel flags but it didn't change anything.
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>GraphicsEnabler</key> <string>No</string> <key>Kernel Flags</key> <string>arch=i386 -v -f -force32</string> </dict> </plist>Go to the full post