A: This is the first version of OS X to offer a 64-bit kernal mode. This is also the first version to require an Intel processor; it will not run on G5 or earlier processors. Both 32-bit and 64-bit operation are supported, in order to provide backward compatibility with existing applications. This version of Mac OS X is about 7GB smaller than the previous Leopard (10.5) version. Numerous other enhancements and improvements have also been added, and the speed of the OS and 64-bit applications should be greatly increased.