Just as clarification, 32-Bit Systems can only access 2^32 different Addresses, that's exactly 4294967296, or 4 Billion, or 4 Giga
With 64-Bit you'll be theoretically able to adress 2^64 Addresses, so that opens enough room for 4 Billion x 4GB, or 16EB (ExaByte) of Memory, which should be enough for a while
