Short for Intel's Physical Addressing Extensions, a scheme developed for 32 bit Intel x86 CPUs such as the Xeon to permit addressing of more than 4 Gigabytes of memory.

Practically speaking, PAE permits a system with (say) 32GB of physical memory to make up to 3GB available to user level processes. Using more memory than this requires special programming to handle the awkward 36-bit addressing modes; IBM for example, has ported DB2 to use a large amount of memory.

Such kludges are reminiscent of the painful period when we last bumped up against memory limits. Remember Himem or 640k? Such worries will hopefully disappear soon, given the advent of 64 bit computers (e.g., the Mac G5 or AMD's Opteron), which do not suffer such restrictions.

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