what does mac leopard's 64-bit mean (in english please)?

Answer 1

It means it is better than the older 32-bit version.

It is in theory double!

But by being a mac - it is inherently less usefull than a 486 running Windows 95.

But even so - it means it's a better Mac than a 32-bit version.

If it's anything like windows - some programs only work on 64 bit machines, and vice versa. So some old programs wont work. But normally you can solve those sort of problems.

Answer 2

There are many aspects of an operating system and a processor chip that make it 64-bit. For the IBM and Intel processors used by Apple, it means 64-bit register and 64-bit addressing. But in simple terms it means a wider stream of data. This could be compared to a river. If there were two rivers, each the same depth of water but one river was twice as wide as the other, the wider river would allow twice as much water to flow. In the computer system, a wider data path means info will flow through the system faster. Even if two processors are the same "speed" (for example, 2.5 GHz), the 64-bit processor will move info faster than the 32-bit processor. But the operating system should be 64-bit compatible as well as the particular other applications or things go back to 32-bit flow rate.

Many applications (another name for programs) are 32-bit design. Backward-compatibility of the system with older 32-bit applications is a useful feature of the processor and the OS version so you won't have to buy all new applications when you upgrade your OS or computer. Most applications that worked in OS 10.1 also work in OS 10.4 and we expect most of them to work in 10.5.

By the way, 64-bit-ness is somewhat incremental. The first PowerPC processors designed by Apple-IBM-Motorola consortium for the 1994 Apple systems were 64-bit aware. I have OS X installed on a computer with an old 604e processor (1997) and it has no problems. The best processor used by Apple now, the G5, is a full-feature 64-bit chip.

OS 10.3 was more 64-bit capable than 10.2 and 10.4 is almost fully 64-bit capable. Leopard (10.5) should take things up another notch. What we get from Apple is a super-high-tech design from fundamental EFI architecture (no BIOS) through the processor to the operating system. Microsoft cannot go this far in high-performance design since they are beholden to a dozen other companies making old-style BIOS PCs and old-style 32-bit processors. This doesn't mean you can't buy an EFI board with an AMD 64-bit processor. It just means you need to put OS X on it somehow or you're far below the bar.