Windows 2000 Datacenter Server Does Not Locate Memory Greater Than 16 GB (292934)

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When a computer is started with the /3gb switch, the kernel space is limited to 1 GB of memory and properly compiled programs are able to allocate up to 3 GB of memory rather than the 2 GB of memory that can normally be allocated by a program.

When a computer is started with the /pae switch, the size of the Page Table Entry (PTE) increases from 4 KB to 8 KB. The number of PTEs that are required when you translate memory is increased as the amount of memory in a computer increases.

When the /3gb switch is used, the kernel mode space is limited to 1 GB rather than the usual 2 GB amount. When a computer contains large amounts of memory, the combination of reduced kernel space, increased PTE size, and increased PTE utilization can cause a server to be unable to index any additional memory and can cause the server to stop responding.

When a computer is started and the presence of the /pae and /3gb switches are detected, the operating system does not recognize any memory above 16 GB. If you start the computer without the /3gb switch, the computer is enabled to locate all available memory up to 32 GB. This behavior protects the stability of the operating system from known conditions and the limitations of providing support for large memory configurations on a 32-bit platform.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base: More information is available at the following Microsoft Web sites:

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