Win32-bit vs. Win64-bit

Comparison of 32-bit and 64-bit memory architecture for 64-bit editions of GVS9000 Windows XP and Windows Server 2003

Following table, the increased maximum resources of GVS9000 that are based on 64-bit versions of Windows and the 64-bit Intel processor are compared with existing 32-bit resource maximums.

Architectural component
64-bit Windows
32-bit Windows
Virtual memory 16 terabytes 4 GB
Paging file size 512 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 memory

This is a method of extending the available physical memory on a GVS9000. 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 GVS9000 in addition to the size of the pagefile.

Paging file

This is a disk file that the GVS9000 uses to increase the amount of physical storage for virtual memory.


This is a special region that is used to map the process working set list and to temporarily map other physical pages for such operations as zeroing a page on the free list (when the zero list is empty and the zero page is needed), invalidating page table entries in other page tables (such as when a page is removed from the standby list), and in regards to process creation, setting up the address space of a new process.

Paged pool

This is a region of virtual memory in system space that can be paged in and out of the working set of the system process. Paged pool is created during system initialization and is used by Kernel-mode components to allocate system memory. Uniproccessor systems have two paged pools, and multiprocessor systems have four. Having more than one paged pool reduces the frequency of system code blocking on simultaneous calls to pool routines.

Non-paged pool

This is a memory pool that consists of ranges of system virtual addresses that are guaranteed to be resident in physical memory at all times and thus can be accessed from any address space without incurring paging input/output (I/O). Non-paged pool is created during system initialization and is used by Kernel-mode components to allocate system memory.

System cache

These are pages that are used to map open files in the system cache.

System PTEs

A pool of system Page Table Entries (PTEs) that is used to map system pages such as I/O space, Kernel stacks, and memory descriptor lists.

The 2-GB user-mode virtual memory limitation

64-bit programs use a 16-terabyte tuning model (8 terabytes User and 8 terabytes Kernel). 32-bit programs still use the 4-GB tuning model (2 GB User and 2 GB Kernel). This means that 32-bit processes that run on 64-bit versions of Windows run in a 4-GB tuning model (2 GB User and 2GB Kernel). 64-bit versions of Windows do not support the use of the /3GB switch in the boot options. Theoretically, a 64-bit pointer could address up to 16 exabytes. 64-bit versions of Windows have currently implemented up to 16 terabytes of address space.