[liuliu]

Several reasons for me because that my desktop computer are mainly used to run several scientific computing tasks.

1. It can provide performance boost if you take advantage of that 64-bit calculation (two 32-bit calculations) is done in one clock-cycle, you can actually achieve 100% speed up.

2. Use more than 4G memory is not a big deal in scientific computing, and let's face it, more memory is better than read from disk.

3. The argument about the double memory consumption is plain wrong. All program still use int as the main type, which only 32-bit long. Only pointers takes 64-bit long, but you don't save much pointers in your memory (what's the point of keep 4G pointers in memory anyway?). Thus, the memory consumption is little larger, but definitely manageable.

4. (This point may be wrong, please correct me) double precision is common for calculation, and it takes exact 64-bit long, which makes it more suitable for 64-bit CPU.