PAE

PAE, or Physical Address Extension, is an acronym with multiple meanings, most prominently in computing and electronics. In computing, Physical Address Extension refers to a feature of IA-32 processors that expands the addressable physical memory beyond 4 GB. By using a 36-bit physical address rather than 32 bits, a 32-bit system can address up to 64 GB of RAM. PAE was introduced by Intel in the mid-1990s with the Pentium Pro and changes the page-table structure to support the larger address space while maintaining compatibility with existing 32-bit software.

The practical effect of PAE depends on the operating system. Some systems expose PAE to enable more than 4 GB of RAM on 32-bit hardware, while others do not enable or require it. Linux, for example, commonly provides a PAE-enabled kernel for systems that need more memory. Windows and other operating systems have offered varying levels of PAE support across editions and versions, but the underlying memory model remains 32-bit virtual addressing with a larger physical address space in PAE mode.

In RF engineering, PAE also stands for power-added efficiency, a metric used to evaluate the efficiency of a power amplifier. It is defined as (Pout − Pin) / Pdc, where Pout is the RF output power, Pin is the input RF power, and Pdc is the DC power drawn from the supply. This usage is unrelated to memory addressing but is a common acronym in communications design.

Overall, PAE most often denotes Physical Address Extension in computing, with a secondary but separate meaning in electronics as power-added efficiency.