'Tiger obliterates that restriction and allows applications to access a 64-bit address space when running on the PowerPC G5. Therefore, not all parts of an operating system may use the latest x-bit technologies.Īpple, like others, has gradually introduced portions of 64-bit functionality into their most recent operating systems. Advances in processor technology take time to be properly integrated into both existing and future systems. 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.Īn operating system can take advantage of the range of values offered by modern 64-bit processors, but it isn't quite as simple as just creating a new version of the OS after turning on the 64-bit switch. 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. This processor had 8-bit registers, and had a 16 bit memory address space. Let's start with a simple example, the 6502 in the first Apple ][ computers.

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. The terms '64-bit processor' and '64-bit operating system' get tossed around quite a bit, but the exact definition isn't exactly clear. Everyone seems to be tossing around the term 64-bit, and it can get confusing. 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.

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