I have a few 64 bit machines.  At least two of them are actually running 64bit operating systems.  My Mac is merely 64bit compatible or ready or I forget what they claimed.  (Mac goes 64bit with 10.6, but 10.4 and 10.5 are, you know, fully prepared for it.)

The big advantage with 64bit systems is that you have instant access to RAM in excess of 4GB (really about 3.5GB or so).  Of course you could accomplish nearly the same thing by enabling PAE in the kernel, but never mind that for the moment.

Mostly applications are still 32bit and really couldn’t care less about the whole 64bit thing.  Some applications are—don’t shake your head—64bit ready.

AMD (as of 2003) and Intel (as of 2005) have fully comitted to making 64bit processors, and by “fully commited” I mean they began making processors that were at least ready if not actually 64bit.

I only started this little investigation because I couldn’t get Thunderbird working properly on my 64bit Ubuntu 10.04 machine.

Oh, but I’ve been rambling on too long.  I found this nice article to talk about it and you should read that because it’s much better than I could write at this point and my head hurts from thinking about address space extensions.

After you read the article you can drop in and tell me your thoughts and lamentations.