|Architectural component||64-bit Windows||32-bit Windows|
|Virtual memory||16 terabytes||4 GB|
|Paging file size||256 terabytes||16 terabytes|
|Hyperspace||8 GB||4 MB|
|Paged pool||128 GB||470 MB|
|Non-paged pool||128 GB||256 MB|
|System cache||1 terabyte||1 GB|
|System PTEs||128 GB||660 MB|
Virtual memoryThis is a method of extending the available physical memory on a computer.
In a virtual memory system, the operating system creates a pagefile, or swapfile, and divides memory into units called pages. Recently referenced pages are located in physical memory, or RAM.
If a page of memory is not referenced for a while, it is written to the pagefile. This is called "swapping" or "paging out" memory. If that piece of memory is then later referenced by a program, the operating system reads the memory page back from the pagefile into physical memory, also called "swapping" or "paging in" memory.
The total amount of memory that is available to programs is the amount of physical memory in the computer in addition to the size of the pagefile. An important consideration in the short term is that even 32-bit applications will benefit from increased virtual memory address space when they are running in Windows x64 Editions.
Applications that are compiled with the /LARGEADDRESSAWARE option, as would be required to take advantage of the /3GB switch in 32-bit Windows, will automatically be able to address 4 GB of virtual memory without any boot time switches or changes to x64 Windows. Plus, of course, the operating system does not have to share that 4 GB of space. Therefore, it is not constrained at all.