alephnull on 07 November 2009
| Rath said: @Uber. Doesn't 64 bit also require far more address space though? Also does 64 bit mean double word size? |
64-bit instructions allow for a virtual address space of 2^64 bytes so you don't necessarily need 4GB+ to take advantage of it.
A major disadvantage is that all pointers now take up 8 bytes instead of 4 bytes. A linked list could theoretically take up twice as much memory in 64-bit mode.
The real advantage of using 64-bit instructions is the increase of directly addressible registers. The HPC people like it for it's high precision friendly features, for example it also eliminates alignment issues with doubles.
