no obvious benefits I think. (at least from the user perspective)

I once read that the leap from 16 to 32-bit was much bigger than the change from 32-bit to 64-bit. Apparently, numbers that are so big that they would need 64-bit to fit into one register are not very common. Hence, speed increase is only marginally, I guess.

32bit simplified memory addressing
multiple 64kB segment -> 4GB linear address space

For the moment, only a few people really need 4GB

What does 64 bit mean?

Well we've been using 64bit since SSE/MMX really but only in terms of parallel register processing. The Nintendo 64 and Atari Jaguar had 64bit processors as far back as the late 90s but these served mainly as 'fat pipes' between their different system cores (GPU, SPU, CPU) and memory - what the production teams cut in raw power and speed they could make up in 64bit bus bandwidth.

MiniMax wrote:

What does 64 bit mean?

I think it means bigger registers for the microprocessor (64bit wide) so it can compute bigger numbers per instruction and also allowing bigger memory addressable space. I think Windows XP (32bit) is limited to 3GB maximum RAM but I am not sure. Supposedly, 64bit PCs+64bit Operating Systems could address larger amounts of RAM and also have the bigger instruction registers for programmers (more efficient code when properly compiled - I am guessing bigger register can do "much more" per instruction cycle). Just as Qbix said: not that much of a difference from an user point of view.

.... which makes the answer to Kreshnas question about "why haven't we seen too many O/S, apps, and especially games, moving to 64 bit?" quiet obvious:

Games don't have much need for handling integers or floating point numbers that exceeds the current 32 bit registers, and they certainly don't need to access more than a few gigabytes of data.

I heard that to get the "Games for Windows" logo on the box is that the game has to have both 32bit/64bit versions. Not sure how true that is.

During the transition 16bit->32bit, PCs were running dos
It was easy to make 32bit programs without installing a newer os since in real mode, nothing prevented switching to pmode.

With XP, I don't know if it is possible to run 64bit code from 32bit version.

DosFreak wrote:

I heard that to get the "Games for Windows" logo on the box is that the game has to have both 32bit/64bit versions. Not sure how true that is.

Not true. To get the "Games for Windows" logo slapped on the game it needs to work as intended in 64bit Vista, but it can still be a 32bit executable.

I wonder whether any consumer based computing product can truly boast 64-bit addressing space. That is 16 exabytes of memory addressing space, a truly gargantuan number. Just remember it took at least 15 years for the 32-bit addressing space, first introduced (1985) in consumer-level hardware in the Intel 80386, before that was really getting cramped.

dh4rm4 wrote:

Well we've been using 64bit since SSE/MMX really but only in terms of parallel register processing. The Nintendo 64 and Atari Jaguar had 64bit processors as far back as the late 90s but these served mainly as 'fat pipes' between their different system cores (GPU, SPU, CPU) and memory - what the production teams cut in raw power and speed they could make up in 64bit bus bandwidth.

wrong, the N64 had two 32bit processors but was advertised as 64bit.

Wrong. The N64's MIPS R4300i was and still is a 64bit processor.

"MIPS R4300i 64-bit RISC CPU running at 93.75MHz (1.5X bus multiplier)"

from : http://n64.icequake.net/#n64