Q. Physical Address Extension (PAE) refers to a feature of x86 and x86-64 processors that allows more than 4G bytes of physical memory to be used in 32-bit systems. The x86 architecture presently uses only 36 bits out of 52 bits possible. On x86-64 processors, PAE is obligatory in native long mode; currently 40 bits are used out of 52 bits possible. How do I find out if my Linux kernel supports 36-bit or more physical addressing?
A. You can easily find this information by visiting /proc/cpuinfo file. cat /proc/cpuinfo and look for the physical address size. You can also use grep command extract exact information:
cat /proc/cpuinfo
OR
grep physical /proc/cpuinfo
Sample output:
physical id : 0 address sizes : 36 bits physical, 48 bits virtual physical id : 3 address sizes : 36 bits physical, 48 bits virtual physical id : 0 address sizes : 36 bits physical, 48 bits virtual physical id : 3 address sizes : 36 bits physical, 48 bits virtual
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{ 3 comments… read them below or add one }
Not worked on Debian etch with Xeon processors.
This doesn’t work on ubuntu 8.10 either.
~$ grep physical /proc/cpuinfo
physical id : 0
physical id : 0
Address sizes isn’t displayed.
Some info: The generic kernel doesn’t support more than 3GB RAM. the “server” kernel does support it.
Can you give more information about current kernel and CPU? This is more applicable to 64 bit XEON CPUs.