Mac OS X Snow Leopard

If you’re wondering why there’s all this talk about bits, especially with the upcoming introduction of Mac OS X 10.6, aka Snow Leopard, you’re not alone. Everyone seems to be tossing around the term 64-bit, and it can get confusing. The terms “64-bit processor” and “64-bit operating system” get tossed around quite a bit, but the exact definition isn’t exactly clear. Let’s try to tear apart this mess.

Processor

The processor is the brain of your computer, and best deals with information in chunks which are, as you may have guessed, a certain number of bits in length. Let’s start with a simple example, the 6502 in the first Apple ][ computers. This processor had 8-bit registers, and had a 16 bit memory address space.

This means registers could represent 256 (2^8) values, and there are 64K (2^16) memory locations, each of which holds an 8-bit byte. Fast forward to the latest Core 2 Duo processors, whose registers can represent 2^64 values, and can address up to 2^64 bytes of (virtual) memory. (continue reading…)