Originally Posted by Krazy Owl
I tought it was related to the processing power and bandwith like videocards with their 64-128-256 bits.
nope not at all
gpus use a custom buss for communication between the gpu-core and its onboard ram(think Hyper transport link) the wider this path the faster the gpu can access its onboard ram == performace
in cpu's 64bit refers to the amount of "address space" that the cpu can access and its corresponding registers
x64 also allows a more efficient management or LARGE amounts of ram/certain caches
moar bits allow the data to be processed in bigger chunks so if you have a app that can use more then 2GB of ram or so then you will see a benefit but if you don't run apps that need that much access to ram or need to use a lot of cpu registers at once its actually slower by a few% because of the amount of overhead you add when running under x64(64bit processes use more ram)