A big win for 64bit java over 32bit is that the kernel can provide more memory to the 64 bit process. This is because the java heap has to be 'contiguous' memor

A big win for 64bit java over 32bit is that the kernel can provide more memory to the 64 bit process. This is because the java heap has to be 'contiguous' memory, and this is difficult to offer when in 32 bit mode due to memory fragmentation. In 64 bit mode the kernel can cobble together disparate blocks of memory and make it appear contiguous to the process.