Core i7 27" imac not going into 64bit mode

Question

i received my 27" Core i7 when they first shipped. love the machine. that said when i hold the 6 and 4 down at boot it does not go into 64 bit mode. what could be causing this and how could a force it into that mode?

Answer 1

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>