The following sections discuss advantages and disadvantages of 64–bit performance.
Arithmetic and logical operations on 64-bit quantities are more efficient.
Operations use full-register widths, the full-register set, and new instructions.
Parameter passing of 64-bit quantities is more efficient.
Parameter passing of small data structures and floating point quantities is more efficient.
Additional integer and floating point registers.
For amd64, PC-relative addressing modes for more efficient position-independent code.
64-bit applications require more stack space to hold the larger registers.
Applications have a bigger cache footprint from larger pointers.
64–bit applications do not run on 32–bit platforms.