- Joined
- Sep 28, 2004
This post is intended to be a handy quick reference to address common questions concerning Windows operating systems and large amounts of installed memory. If anyone would like to add to it, make a correction, or a suggestion, just post or PM me and I will edit it.
Common Question: "I installed four gigs of ram in my computer but Windows says I only have 3.12!"
Cause: All 32bit processors and OSs support 32bits of physical address space which allows software to address a total of 4GB. However, your BIOS reserves space for your graphics card and other peripherals, as does (sometimes) some of your drivers. Why? “This is because some physical address space must be reserved as I/O regions for memory mapped peripherals. These I/O regions are allocated between the 3 GB physical address and the 4 GB upper physical address limit. Physical memory addresses that are mapped to these I/O regions cannot be used to address physical system memory. These addresses also cannot be used to prevent the operating system from using some physical memory that would ordinarily be accessed between the 3GB physical address and the 4GB upper physical address limit. The size of these I/O regions varies from system to system because they determine the type and configuration of the system’s peripherals.” MS Link
Solution 1: If your processor supports x64 extensions, here’s a list, then the technically superior method is to load a 64bit version of the OS you want to use. Sometimes this incurs a small upgrade fee from MS, sometimes it involves buying a new OS outright. Depending on which version of Windows you buy, you can address up to 128GB of RAM.
Solution 2: Use PAE Mode. PAE is another way to address more than 4GBs or RAM; up to 128GBs in a 32bit environment. This method is limited to select versions of Windows Server only.
Note: Vista SP1 will report how much memory is physically installed on the machine, as opposed to how much is available to the OS. MS Link
Note: Systems with more than 4GBs of ram cannot be put into Hibernation. MS Link
Note: 32bit versions of Windows allow only 2GB of memory per process. However, some applications can take advantage of a feature available in select versions of Windows which allows the use of 3GB of RAM to be allocated to the user-mode process. This feature can also be utilized to allot 4GBs of ram to a 32bit processs within a 64bit environment. MS Link, MS Link
Note: 16bit programs will NOT work in a 64bit environment. Keep in mind that the installer for some 32bit applications are 16bit.
Note: If you have 4GBs of RAM and a 64-bit version of windows but it still reports 3.xx, then run msconfig from the Run prompt. Within the System Configuration Utility, navigate to the 'BOOT.INI' tab, click the 'Advanced Options' button. Make sure the '/MAXMEM=' option isn't checked. If it is checked, uncheck it and reboot.
Common Question: "I installed four gigs of ram in my computer but Windows says I only have 3.12!"
Cause: All 32bit processors and OSs support 32bits of physical address space which allows software to address a total of 4GB. However, your BIOS reserves space for your graphics card and other peripherals, as does (sometimes) some of your drivers. Why? “This is because some physical address space must be reserved as I/O regions for memory mapped peripherals. These I/O regions are allocated between the 3 GB physical address and the 4 GB upper physical address limit. Physical memory addresses that are mapped to these I/O regions cannot be used to address physical system memory. These addresses also cannot be used to prevent the operating system from using some physical memory that would ordinarily be accessed between the 3GB physical address and the 4GB upper physical address limit. The size of these I/O regions varies from system to system because they determine the type and configuration of the system’s peripherals.” MS Link
Solution 1: If your processor supports x64 extensions, here’s a list, then the technically superior method is to load a 64bit version of the OS you want to use. Sometimes this incurs a small upgrade fee from MS, sometimes it involves buying a new OS outright. Depending on which version of Windows you buy, you can address up to 128GB of RAM.
Solution 2: Use PAE Mode. PAE is another way to address more than 4GBs or RAM; up to 128GBs in a 32bit environment. This method is limited to select versions of Windows Server only.
Note: Vista SP1 will report how much memory is physically installed on the machine, as opposed to how much is available to the OS. MS Link
Note: Systems with more than 4GBs of ram cannot be put into Hibernation. MS Link
Note: 32bit versions of Windows allow only 2GB of memory per process. However, some applications can take advantage of a feature available in select versions of Windows which allows the use of 3GB of RAM to be allocated to the user-mode process. This feature can also be utilized to allot 4GBs of ram to a 32bit processs within a 64bit environment. MS Link, MS Link
Note: 16bit programs will NOT work in a 64bit environment. Keep in mind that the installer for some 32bit applications are 16bit.
Note: If you have 4GBs of RAM and a 64-bit version of windows but it still reports 3.xx, then run msconfig from the Run prompt. Within the System Configuration Utility, navigate to the 'BOOT.INI' tab, click the 'Advanced Options' button. Make sure the '/MAXMEM=' option isn't checked. If it is checked, uncheck it and reboot.
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