file /System/Library/Extensions/*.kext/Contents/MacOS/* | perl -nle 'print $1 if /\((.*)\)/' | sort | uniq -c

Above  command will take a few seconds to run.

Comparison between 10.5.8 and 10.6.0.
10.5.8

109 for architecture i386
106 for architecture ppc
3 for architecture ppc7400


10.6.0

135 for architecture i386
38 for architecture ppc
127 for architecture x86_64


You can also look at “Extensions” in the “Software” section of the System Profiler utility. (Select Apple Menu->About This Mac and then click “More Info”). One of the columns shows whether the .kext is 64-bit capable. Only those extensions that are not 64-bit will show up with a “No” in that column.

Wondering how many 64-bit and 32-bit extensions in Snow Leopard is a post from: My MacOS X

# ioreg -l -p IODeviceTree | grep firmware-abi

The response will identify the machine as either having 32-bit or 64-bit EFI.

To boot 64-bit kernel every time you boot machine:

1. Print nvram settings

# sudo nvram -p

2. Set boot-args to use 64 bit kernel

# sudo nvram boot-args="arch=x86_64"

Don’t forget to add in your existing boot-args to the command above. Using nvram means you don’t need to have to remember to hold down 6 or 4 during booting each time. To go back to the 32 bit kernel, just set the boot-args using nvram without the arch=x86_64 option.

Boot Snow Leopard into the 64-bit kernel is a post from: My MacOS X