|Yes, it will require more memory from time-to-time, but it's not cut & dried. The reason M$ is suggesting at least twice as much memory is to allow for adequate contingencies since your 64-bit Windows comprises 32-bit libraries as well as 64-bit libraries for 32-bit app compability ... see below.|
"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. Maintaining a partial 32-bit model is one way to handle this and is in general reasonably effective. In fact, the highly performance-oriented z/OS operating system takes this approach currently, requiring program code to reside in any number of 32-bit address spaces while data objects can (optionally) reside in 64-bit regions."
Windows 7 News!