> When 16 bit computers went to 32 bit, people probably thought that one wouldn't ever need 64 bit computers either. People have said that about pretty much ev

> When 16 bit computers went to 32 bit, people probably thought that one wouldn't ever need 64 bit computers either. People have said that about pretty much every memory size in the history of computing. The argument for 64-bit is not "2^64 bytes ought to be enough for anyone"; it's "you couldn't use more than 2^64 bytes even if you wanted to". Writing a full register worth of data every clock cycle at 4GHz works out to 32GB/s. (2^64B / 32GB/s) is just over seventeen years, to fill up a 64-bit address space, assuming you're doing no actual computation. Few computers even work for seventeen years without replacement, much less run single processes continually with no reboots.