"The main disadvantage of 64-bit architectures is that relative to 32-bit architectures the same data occupies more space in memory (due to swollen pointers and possibly other types and alignment padding). This increases the memory requirements of a given process and can have implications for efficient processor cache utilization. {source}
Or from Apple's own documentation:
Myth: My application will run much faster if it is a ""native"" 64-bit application. Fact: Some 64-bit executables may run more slowly on 64-bit Intel architectures because of increased cache pressure. {source}
Many core apps have been rewritten as 64bit. That means more memory will be needed by those apps overall. I can't see how Snow Leopard will use less memory than Leopard, unless apple have made some significant optimisations elsewhere (as MS did going from Vista > Win7)."
"Snow Leopard is all about optimization. Apple's goal is for everything to run faster on existing hardware. So, if anything, Snow Leopard will probably consume LESS RAM :)
