Booting into 64bit mode with Mac Pro 2009

Question

I am trying to boot into 64bit mode with a 2009 Mac Pro 2.93 Quad core machine. I tried holding down 6 and 4 when restarting but no luck, it staill says no in the profiler. Any ideas why?

Answer 1

If you'd like your Mac to always start up in 64 bit mode without having to hold down any keys, do this:
Here's the configuration file approach for always booting into 64-bit. This is the best way to make your Mac always start up 64 bit as the only thing necessary is to alter one line of a configuration file. You can do that by opening the Terminal and entering:
sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.Boot 'Kernel Flags' 'arch=x86_64'
To return to 32 bit mode, you would repeat the command but enter an empty string, which would just be the single quotes (where arch=x86_64 is) with nothing in between.
sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.Boot 'Kernel Flags' ''
These commands are all one line, they're just wrapping here.
If at any point you find you need to start up in 32 bit mode for a single use, just as you held down the 6 and 4 keys for 64 bit, you can hold down the 3 and 2 keys for a temporary change. No need to keep changing the config file over and over.