64-Bit Processing and X-Plane

A common question is, "When will X-Plane be compiled as 64-bit, to natively support 64-bit systems?"

The answer is not quite what one might think, because 64-bit processing does not really give more speed. Here is what it does:
 * 1) It allows access to more than 2 GB of RAM. Since X-Plane only uses half this much RAM, though, this function is not useful to X-Plane.  Why have access to RAM the simulator will not use?
 * 2) It allows "bigger numbers" to be used natively in some cases, thus allowing the program to work with 64-bit numbers. Again, though, when does X-Plane need or even want a 64-bit number?  Never!  8-bit numbers are fine for 99.9% of cases, and 16-bit numbers are needed for the other 0.1% of the time when we need really high precision.  There is no a need for a single 64-bit number in the entirety of X-Plane!

We went through this years ago with MMX. Everyone would ask "When do I get MMX? When do I get MMX?". When MMX was finally enabled, though, the frame rate gain was so tiny that it was not even worth having. This is because MMX did not actually address the stuff in X-Plane that actually took the most time—moving polys across the bus to the video card. Now we are going through this again with 64-bit operating systems. It sounds interesting, but, for now, there is no reason to have it in X-Plane because it is not useful for the kinds of things the simulator does.

Some day, this will change, of course, like when X-Plane uses more than 2 GB of RAM, or when it uses the sun, rather than the Earth, as its coordinate reference to allow real-time, engineering-accurate flights to Mars. It will be useful when X-Plane uses the galactic center, rather than the Sun, as its coordinate reference to allow engineering-accurate flights to other star systems. We'll need some big, big numbers then, and 64-bit operating systems will be needed to get the job done.

For now, for most home users, 64-bit OSs are all hype. When X-Plane can take advantage of native 64-bit compiling, it will.

Note, of course, that X-Plane will run on a 64-bit operating system—it will do so as a 32-bit application only, though.