What Does the Number of Bits in Physical Address Extensions (PAE) of Memory Specifications on Intel® Xeon® Processors Mean?

The number of bits in the physical address extensions (PAE) of memory specifications on Intel® Xeon®  Processors dictates the maximum addressable physical memory space that the processor can handle. For detailed information about the Processors, go to Intel® Xeon® Product Specifications.

Here is a step-by-step breakdown:

1. Physical Address Bits: This indicates the number of bits used by the processor to address physical memory. For example, if a processor supports 52 physical address bits, it can theoretically address up to 2^52 bytes of memory.

2. Virtual Address Bits: This indicates the number of bits used by the processor to address virtual memory. For example, if a processor supports 48 virtual address bits, it can address up to 2^48 bytes of virtual memory.

3. Memory Address Calculation:

   • For a processor with 52-bit physical addressing, the maximum addressable physical memory is 2^52 bytes.
   • For a processor with 48-bit virtual addressing, the maximum addressable virtual memory is 2^48 bytes.

4. Practical Implications:

   • Having more physical address bits allows a processor to support larger amounts of RAM, which is critical for high-performance and memory-intensive applications.
   • More virtual address bits enable the processor to handle larger and more complex applications, as it can manage more virtual memory space, which the system can map to physical memory as needed.

For example, the Intel® Xeon® Scalable Processors support up to 46 bits of physical address space and 48 bits of virtual address space, allowing significant memory addressing capabilities.

In summary, the number of bits in physical address extensions directly impacts the processor's capability to support large physical and virtual memory sizes, enhancing its performance and scalability for demanding applications.

As this feature is dependent on the Operational System, for more details, check Physical Address Extension - Win32 apps | Microsoft Learn.