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What's the command to find out if PAE is enabled ?

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2 Answers 2

Firstly, your CPU needs to support it:

[madhatta@www ~]$ grep -i pae /proc/cpuinfo 
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
                                     ^^^

Secondly, your kernel needs to support it. For CentOS, this is built into the kernel version string:

[madhatta@www ~]$ uname -r
2.6.18-194.32.1.el5PAE

Your distro may have different policies, so if you can tell us what you're running, we may be able to be more help.

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Check your kernel options:

egrep "HIGHMEM|X86_PAE" /boot/config-`uname -r`
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Forgive me, cakemox, but I think PAE is CONFIG_X86_PAE; your grep, while excellent, identifies HIGHMEM support, which I think is something slightly different. –  MadHatter Mar 14 '11 at 11:27
    
CONFIG_HIGHMEM64G implies CONFIG_X86_PAE. I'm not sure CONFIG_X86_PAE will always show up when selected as CONFIG_HIGHMEM64G. Probably safest to look for both. –  Cakemox Mar 14 '11 at 11:43
    
I stand corrected; thank you! –  MadHatter Mar 14 '11 at 13:43

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