BCDEdit /set increaseuserva

/3GB on “Windows 2000 Professional” and “Windows 2000 Server” has the effect of reducing kernel size to 1 GB while the application address-space stays 2 GB.

Application must have IMAGE_FILE_LARGE_ADDRESS_AWARE in its header to get an 3GB address-space. This is for backward compatibility with old programs which compare pointers (pointers are signed)

Some DLL’s load at 2GB boundary (0x7FFFFFFF and below). This makes it impossible to have an continues address-space above 2GB. A VirtualAlloc above 2GB will fail therefore.

/PAE Enable enhanced adressing mode (36bit physical addressing mode, max 64GB theoretically)

Minimum processor for PAE: Intel Pentium Pro (AMD x64)
/USERVA: reduce the user-address-space from 3GB downto 2GB to leave more memory for the kernel

Why less than 4GB is seen by 32-bit Windows XP (and other 32-bit OS which support max 4GB and no PAE)
An Intel-architecture processor (AMD included) maps I/O ports onto memory addresses. In the design of the PC the PCI/AGP I/O is started from address 0xFFFFFFFF and lower addresses. The 0xFFFFFFFF is the max address of 32bit (4GB). The size of this I/O address range is depends on the detailed design of the motherbord, BIOS and of the present PCI/AGP cards.
Memory at these I/O address range cannot be addressed. Modern motherboards have a remapping option so the memory located at the I/O addresses is moved to addresses above the 0xFFFFFFFF (4GB) address. Unfortunately 4GB-32bit-Windows versions (like XP) is not able to address memory located above the 4GB boundary, now for another reason as the kernel uses 32bit words for addressing.. With PAE (uses 36bit adresses) addressing is possible but PEA is not supported by the 4GB-versions of Windows.

Take for example a ASUS M2N motherboard with 8GB memory with a Geforce 8500 PCI-e card and 3 SATA x4 controllers.

The remapping option can be found at BIOS->Advanced->Chipset->Memory controller->Memory configuration->Memory hole remapping.

The I/O on this motherbord is located from 0x9FF49000 to 0xFFFFFFFF. Only the first 2683604992 bytes of memory can addressed below the 4GB boundary. The remapping option remaps the memory between 0x9FF49000-0xFFFFFFFF to the addresses 0x100000000-0x1600B7000. We see the following:

• 
  Without remapping 1536MB of memory is not seen by the BIOS as it is located at I/O addresses
  
• 
  Remapping makes no difference for 4GB-32bit Windows as the remapped memory is out of reach. Always 1536MB is unused.
  
• 
  On 64bit Windows or 32bit Windows with PAE the remaping results in 8GB of available memory (ca. 2MB less because of resevered kernel and BIOS memory).
  

• 
  Europe Vista versions do not have media player and media API’s (and that last one makes them unusable of course)
  
• 
  A 64bit application’ virtual addressspace is 8TB (althrough 64bit could address 16777216 TB = 16 EB). Microsoft only reserves a “small” part of the total possible addressspace for applications, because it is so “unbelievable” large… well, the future will tell…
  
• 
  There is no 32bit version of Windows Compute Cluster Server 2003
  
• 
  There are no 64bit versions of Windows 2003 Small Business Server, Windows 2003 Server Web Edition, Windows 2003 Storage Server, Windows 2003 Storage Server Enterprise Edition
  

• 
  GetNativeSystemInfo indicates x86/x64: PROCESSOR_ARCHITECTURE_INTEL, PROCESSOR_ARCHITECTURE_AMD64, PROCESSOR_ARCHITECTURE_IA64, PROCESSOR_ARCHITECTURE_MIPS, PROCESSOR_ARCHITECTURE_ALPHA, PROCESSOR_ARCHITECTURE_PPC, PROCESSOR_ARCHITECTURE_UNKNOWN
  
  
  
• 
  GetProductInfo indicates: PRODUCT_BUSINESS, PRODUCT_BUSINESS_N, PRODUCT_CLUSTER_SERVER, PRODUCT_DATACENTER_SERVER, PRODUCT_DATACENTER_SERVER_CORE, PRODUCT_DATACENTER_SERVER_CORE_V, PRODUCT_DATACENTER_SERVER_V, PRODUCT_ENTERPRISE, PRODUCT_ENTERPRISE_N, PRODUCT_ENTERPRISE_SERVER, PRODUCT_ENTERPRISE_SERVER_CORE, PRODUCT_ENTERPRISE_SERVER_CORE_V, PRODUCT_ENTERPRISE_SERVER_IA64, PRODUCT_ENTERPRISE_SERVER_V, PRODUCT_HOME_BASIC, PRODUCT_HOME_BASIC_N, PRODUCT_HOME_PREMIUM, PRODUCT_HOME_PREMIUM_N, PRODUCT_HOME_SERVER, PRODUCT_HYPERV, PRODUCT_MEDIUMBUSINESS_SERVER_MANAGEMENT, PRODUCT_MEDIUMBUSINESS_SERVER_MESSAGING, PRODUCT_MEDIUMBUSINESS_SERVER_SECURITY, PRODUCT_SERVER_FOR_SMALLBUSINESS, PRODUCT_SERVER_FOR_SMALLBUSINESS_V, PRODUCT_SMALLBUSINESS_SERVER, PRODUCT_STANDARD_SERVER, PRODUCT_STANDARD_SERVER_CORE, PRODUCT_STANDARD_SERVER_CORE_V, PRODUCT_STANDARD_SERVER_V, PRODUCT_STARTER, PRODUCT_STORAGE_ENTERPRISE_SERVER, PRODUCT_STORAGE_EXPRESS_SERVER, PRODUCT_STORAGE_STANDARD_SERVER, PRODUCT_STORAGE_WORKGROUP_SERVER, PRODUCT_UNDEFINED, PRODUCT_ULTIMATE, PRODUCT_ULTIMATE_N, PRODUCT_WEB_SERVER, PRODUCT_WEB_SERVER_CORE, PRODUCT_UNLICENSED
  
  
  
• 
  GetSystemMetrics indicates SM_MEDIACENTER, SM_STARTER, SM_TABLETPC, SM_SERVERR2
  
  
  
• 
  OSVERSIONINFOEX.wProductType indicates VER_NT_WORKSTATION,VER_NT_SERVER,VER_NT_DOMAIN_CONTROLLER
  
  
  
• 
  OSVERSIONINFOEX.wSuiteMask indicates bitmask: VER_SUITE_BACKOFFICE, VER_SUITE_BLADE, VER_SUITE_COMPUTE_SERVER, VER_SUITE_DATACENTER, VER_SUITE_ENTERPRISE, VER_SUITE_EMBEDDEDNT, VER_SUITE_PERSONAL, VER_SUITE_SINGLEUSERTS, VER_SUITE_SMALLBUSINESS, VER_SUITE_SMALLBUSINESS_RESTRICTED, VER_SUITE_STORAGE_SERVER, VER_SUITE_TERMINAL, VER_SUITE_WH_SERVER
  

Remote desktop is a must in order to reach you computer when not at home. There is no advantage of Enterprice/Ultimate on top of Business, except perhaps for Virtual PC support, MediaCenter and MUA support (on-the-flight change of display language, which does not realy change everything anyway). The N-versions are ofcourse in any way unusable.

KB283037: /3GB option

KB810371: /USERVA option, exchange server

KB171793: /3GB option

KB316739: /USERVA option

KB294418: Comparison of 32-bit and 64-bit memory architecture for 64-bit editions of Windows XP and Windows Server 2003

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsqldev/html/sqldev_01262004.asp

http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

http://support.microsoft.com/kb/294418

http://msdn.microsoft.com/en-us/library/ms791558.aspx

http://msdn.microsoft.com/en-us/library/aa906211.aspx

http://msdn.microsoft.com/en-us/library/aa366778.aspx

http://www.microsoft.com/presspass/newsroom/windows/factsheets/WinVistaStarterFS.mspx

Vista versions

http://windowsitpro.com/article/articleid/47669/pre-pdc-exclusive-windows-vista-processor-and-memory-support-revealed.html