memcpy performance differences between 32 and 64 bit processes

Question

We have Core2 machines (Dell T5400) with XP64.

We observe that when running 32-bit processes, the performance of memcpy is on the order of 1.2GByte/s; however memcpy

Answer 1

My off-the-cuff guess is that the 64 bit processes are using the processor's native 64-bit memory size, which optimizes the use of the memory bus.