alt Hacker NewsOn x86-64, you need an extra prefix to do 64-bit operations (while 64-bit addressing is the default), so it's a question of "are you sure you need the 64 bits and 32 isn't enough?"
On x86-64, you need an extra prefix to do 64-bit operations (while 64-bit addressing is the default), so it's a question of "are you sure you need the 64 bits and 32 isn't enough?"