For the crib sheet to that, 64 bit Integer calculations are one of the things that make 64 bit CPUs so great - they can make 64 bit calculations in hardware rather than emulating it with a bunch of 32 bit calculations. The address space is the logical address space the CPU can handle. The AMD64 and EM64T CPUs do not have a full 64 bits of address space, as they won't need it for a while. They use 64 bit addresses and truncate them internally to save on die space.
You can check out this article over here.