[yosh]

Huh? Plenty of things needed more than 4 GB RAM in the 1990s. Scientific and database applications, to name a couple examples. That's why IBM, Sun, HP, SGI, DEC, etc. were all shipping 64-bit machines then. There were also a lot of contortions implemented to make >4 GB happen on 32-bit Intel machines too.

What AMD did (and Intel subsequently copied) with x86-64 was to significantly drop the price of 64-bit capable hardware, to the point where it shipped on personal workstations which didn't really need it then.

[rwmj]

Very true: One thing you've missed is that current x86-64 is not yet providing a true 64 bit address space. Only 44 or 48 bits are provided in shipping hardware. This will no doubt be expanded in later revisions of the hardware, but it seems that 48 bits is enough for even the largest users today.

http://en.wikipedia.org/wiki/X86-64#Virtual_address_space_de...