- Click Start, and then click Run.
- Type X:\boot.ini, where
X is the drive letter of the location of the boot files, Ntldr, Boot.ini, and so forth.
- Modify the line that corresponds to your operating system by appending the /PAE switch.
- Save the file, and then restart the computer.
During a context switch the CR3 register is set by the operating system to point to a Page directory pointer index that is 2-bits wide. The first two bits are used as an index into this table, with the resulting value pointing to a Page directory. The first 9-bit field is then used to index into the Page directory. The indexed value then points to a Page table. The second 9-bit field is an index into the Page table. This value points to the actual page in memory where the desired byte is located. Finding this byte is a simple matter of using the remaining twelve bits of data to index into the page.
If you add more memory, the BIOS may recognize the full amount of physical RAM that is installed on the server. However, Windows will recognize only some of the RAM. If the server includes the Redundant Memory feature, the full amount of RAM is not exposed to Windows. The Redundant Memory feature provides the system with a fail-over memory bank when a memory bank fails. The Memory Mirroring feature splits the memory banks into a mirrored set. Both features are enabled in the BIOS and cannot be accessed through Windows. You may have to see the system user manual or the manufacturer's Web site to modify the settings for this feature.
For example, if you are running a system that has 4 GB of RAM installed, and you add 4 GB of RAM, Windows recognizes 4 GB or 6 GB of RAM instead of the full 8 GB of physical memory. One of these features may be enabled on the new memory banks without your knowledge. In this scenario, the symptoms are similar to the symptoms that may occur when the /PAE switch is not added to the Boot.ini file.
Article ID: 268363 - Last Review: Dec 16, 2009 - Revision: 1