HP Xw6200 FAQs: Windows XP Professional x64 Edition for HP Workstations - Page 5

Windows® XP® Professional x64 Edition for HP Workstations - FAQ 22. WOW64 file and registry redirection, what's that? Windows XP Professional x64 Edition separates 32-bit and 64-bit system and program files and also maintains separate portions of the registry. This is to support running 32-bit application on the 64-bit OS via WOW64 (Windows on Windows). File and registry redirection is typically transparent to the user and 32-bit applications just work. Redirection is more of a concern for application developers, but a brief description of redirection is provided here. Microsoft has details on WOW64 on the Microsoft Developer Network web site, for example, WOW64 implementation details: http://msdn.microsoft.com/library/enus/win64/win64/wow64_implementation_details.asp?frame=true 64-bit Windows system setup installs and registers 64-bit and 32-bit system files. 32-bit system files are copied to "%windir%\SysWOW64" where they are used with WOW64. 64-bit system files are installed to "%windir%\system32". Yes, the 64-bit system files are in a directory called system32 due to legacy issues. Applications are typically separated as well. By default, 64-bit applications are placed in "%SystemDrive%\Program Files" and 32-bit applications are placed in "%SystemDrive%\Program Files (x86)" with the addition of x86 to the directory name. Note that these are just default directories and many application installers allow the end-user to specify a custom directory name which is still supported. Two views of the registry exist on 64-bit Windows: Native and WOW64. By default, a native 64-bit Windows application sees the native registry view, and a WOW64 application sees the WOW64 view. This will separate the 32-bit application state from 64-bit state and provides a safe execution environment for both 32-bit and 64-bit applications. 23. What is the memory limit for Windows XP Professional x64 Edition? Windows XP Professional x64 Edition will support up to 128 GB of RAM. This is a limit imposed by the client OS. (Some x64 versions of Windows Server support larger amounts of memory.) Of course the hardware platform may support more or less RAM. For example, the xw4200 chipset only supports 4GB of RAM so you are limited by the system. 24. How much memory is accessible on a system running XP x64, don't you lose some memory to PCI space and other hardware addresses? The xw workstation can remap the BIOS, PCI space, etc. outside of the space. If a system has 8GB of RAM, Windows XP x64 will be able to access all 8GB. The xw workstation BIOS has a setting that must be enabled to allow for the memory to be remapped. BIOS Setup -> Advanced -> Chipset/Memory -> Memory Remapping = Enable Hardware addresses, PCI, graphics address spaces should not conflict with RAM addresses in the virtual address space. It is possible that a system with 4GB of RAM running Windows XP x64 will see 4GB of usable RAM and a system with 32GB of RAM will see 32GB of usable RAM. Of course this depends on the actual configuration of the system and assumes it has been properly configured. 25. Can a 32-bit application access more memory when running on XP x64? In general no, most standard Windows 32-bit applications or processes are limited to 2GB of virtual address space, the same as in 32-bit XP. Windows 32-bit applications that have been built with the /LARGEADDRESSAWARE switch can access 4GB of RAM. The same application running on Windows XP 32-bit with Service Pack 2 is limited to 3GB of RAM so you gain 1GB of address space on XP x64. Note that a 64-bit application running on XP x64 has 8TB of virtual address space for applications and 8TB of virtual address space for the operating system. Microsoft Windows Professional x64 Edition is currently in beta. The information in this document is subject to change at any time until the OS is officially released. 31 August 2005