At least it had the instruction set. Guess memory sizes were probably too small for 64 bit code.
I don't know if it is very common to have an universal binary with both 32bit and 64 bit. As well as ppc and intel.
Nope. I was wondering about that myself. If you want to see what something is, open up a terminal and run the command "file <whatever>". So, for instance:
$ file /mach_kernel
/mach_kernel: Mach-O universal binary with 2 architectures
/mach_kernel (for architecture i386): Mach-O executable i386
/mach_kernel (for architecture ppc): Mach-O executable ppc
There are a few things that with all 4 architectures, but there aren't many of them.
$ file /Developer/Applications/Xcode.app/Contents/MacOS/Xcode
/Developer/Applications/Xcode.app/Contents/MacOS/Xcode: Mach-O universal binary with 4 architectures
/Developer/Applications/Xcode.app/Contents/MacOS/Xcode (for architecture ppc7400): Mach-O executable ppc
/Developer/Applications/Xcode.app/Contents/MacOS/Xcode (for architecture ppc64)Mach-O 64-bit executable ppc64
/Developer/Applications/Xcode.app/Contents/MacOS/Xcode (for architecture i386):Mach-O executable i386
/Developer/Applications/Xcode.app/Contents/MacOS/Xcode (for architecture x86_64): Mach-O 64-bit executable x86_64