Why is 64bit better?
- 64bit instruction set provides extra registers so code is more efficient. Funny thing though, after all the complaining about x86 having so few registers, we see such a small improvement from these new ones.
- Runs 32bit software just as well as 32bit-only processors. For real.
- Provides >2,3 gigs of address space. If the motherboard supports it. This is good because ram is basically free today.
Why doesn't it matter?
- Do you run a single application today that actually uses more than 2 gigs of ram? For most of you, probably not.
- When an 64bit application runs, all pointers are 64bits (at least on windows). This means that each pointer in the program takes twice as much space.
- This makes for higher contention of data cache and memory bandwidth.
- Pointer intensive apps can slow down significantly when compiled as 64bit, example: spec2k gap
- If the app doesn't need >31bits of address space then it should not be built 64bits, period.
- There is no reason for microsoft to build Office as a 64bit app, it will likely run slower. Sql server on the other hand will care greatly, big databases are very real today, but not for most of you.
- There are very few of you that would benefit from running a 64bit version of photoshop.
- Unless the games are stupidly sloppy, there is no reason for them to be built 64bit. Consider the relative performance of FarCry built 32 and 64bits, no gain, even with the extra registers... There is no mechanical reason for the 64bit version to exist.
Assuming the current growth of address space (and application's ability to consume it) continues at its current insane pace, absolutely my mom will need a 64bit processor in ~5 years, but that is still far after any current pc will have any value.
Anenome: This is very different from the transition from 16 to 32bits. In 16bit time home users were actively managing their memory to stay within the 640k limit. It effected peoples ability to get work done. Folks were screaming for 32bits of address space. My parents have 1gig of ram, run office, photoshop, burn cds, and they never see more than 750megs checked out at a time. They have no issue. Today's relatively sophisticated pc OS performs memory management and insulates most users from the hard constraints of address size.
My opinion: dont worry about 64bit compatibility today. It doesn't matter. Its hype. Don't worry, it will be a long time before you'll be left out in the cold, relegated to the tiny 32bit section at the local software store. I wouldn't turn it down if it were a free upgrade, but I also wouldn't install a 64bit os on it.
As for Multicore? WORRY ABOUT IT, chew your nails. Its great and unlike HT it provides a real speedup. Lots of apps today take advantage of it. User loves it because those background tasks don't interfere with what you're doing. The OS loves it. Virus protection loves it. If you are building applications, you'll love it to no end (parallel builds).
Also, yonah, like the real p4, has SSE3, which rocks. More and more cpu-bound apps will be using that to good effect. Eats up dsp algorithms. Thats the one thing I regret about my xps gen2. I wish it had a yonah.