Did you try a simple pram zap to clear ?
With 32-bit firmware, you cannot boot into 64-bit kernel; it’s not possible.
To determine if your Mac has 32-bit or 64-bit firmware, copy/paste the following command shown in red into Terminal (Terminal is found in the /Applications/Utilities folder):
llcMP:~ lloyd$ ioreg -l -p IODeviceTree | grep firmware-abi | | "firmware-abi" = <"EFI64">
Even if you cannot or do not boot the Mac OS X Snow Leopard kernel into 64-bit mode, you can run your 64-bit apps as 64-bit, and they can take advantage of all the memory in the machine.
Apple has added a command line setting for enabling the 64-bit kernel. You can open a Terminal window and type:
sudo systemsetup -setkernelbootarchitecture x86_64
This is the method I use, because I can leave it set the way I want to; having to hold down '6' and '4' keys at startup is absurd, it’s ridiculous that Apple did not provide a system preference panel for this.
The change is shown in red below (“arch=x86_64”). Use a plain-text editor, such as Text Wrangler.
Edit the file:
/Library/Preferences/SystemConfiguration/com.apple.Boot.plist
Insert arch=x86_64 into the Kernel Flags field.
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>Kernel</key> <string>mach_kernel</string> <key>Kernel Flags</key> <string>arch=x86_64</string> </dict> </plist>
The PRAM method for always booting into 64-bit mode PERMALINK
I’m not a big fan of this method, because I’d rather edit a text file than mess with non-volatile machine settings in the computer itself. This method sets the PRAM (parameter RAM) to tell the machine to boot 64-bi modet. It’s unclear what happens if this is done on a machine that is not 64-bit capable, or if the com.apple.Boot.plist method interacts with it (which overrides which?).
It forces the Mac to always try to boot into 64 bit mode (assuming the boot volume contains a 64 bit kernel).
It can be undone by resetting the PRAM by booting up while holding down the <command>, <option>, 'P' and 'R' keys.
I have not tested this method, you’re on your own here. Open a Terminal window and enter this command:
sudo nvram boot-args="arch=x86_64"
You should be able to reset things as follows:
sudo nvram boot-args=""
Again, I have not tested this.
http://macperformanceguide.com/SnowLeopard-64bit.html
