Any clues here?
https://en.wikipedia.org/wiki/Physical_ ... _Extension
PAE was first implemented in the Intel Pentium Pro in 1995,[2] although the accompanying chipsets usually lacked support for the required extra address bits.[3]
PAE is supported by Intel Pentium Pro and later Pentium-series processors. The first Pentium M family processors ("Banias") also support PAE, however they do not show the PAE support flag in their CPUID information.[4] It was also available on AMD processors including the AMD Athlon[5] (although the chipsets for these were limited to 4 GB RAM[6]) and later AMD processor models.
When AMD defined their AMD64 architecture as an extension of x86, they defined an enhanced version of PAE[7] to be used while the processor was in 64-bit mode ("long mode"). It supports up to 48-bit virtual addresses,[8](p120) 52-bit physical addresses,[8](p24) and includes NX bit functionality. This version of PAE is the mandatory memory paging model in long mode on x86-64 processors; there is no "non-PAE mode" while in long mode.[9] The documentation for "Intel 64", the Intel version of x86-64, refers to these page table formats as "IA-32e paging" rather than "PAE".[10]
Linux
See also: Executable space protection § Linux
The Linux kernel includes full PAE mode support starting with version 2.3.23,[21] enabling access of up to 64 GB of memory on 32-bit machines. A PAE-enabled Linux kernel requires that the CPU also support PAE. The Linux kernel supports PAE as a build option and major distributions provide a PAE kernel either as the default or as an option.
The NX bit feature requires a kernel built with PAE support.[22]
Linux distributions now commonly use a PAE-enabled kernel as the default, a trend that began in 2009.[23] As of 2012 many, including Red Hat Enterprise Linux / CentOS, Ubuntu (and derivatives like Xubuntu and Linux Mint),[24][25][26] have stopped distributing non-PAE kernels, thus making PAE hardware mandatory. Linux distributions which require PAE may refuse to boot on Pentium M family processors because they do not show the PAE support flag in their CPUID information (even though it is supported internally).[4]
Distributions that still provide a non-PAE option, including Debian (and derivatives like LMDE 2 (Linux Mint Debian Edition)[27]), Slackware, and LXLE typically do so with "i386", "i486" or "retro" labels.[28][29]
Here's what dmesg says about the kernel:
root# dmesg
Initializing cgroup subsys cpuset
Initializing cgroup subsys cpu
Initializing cgroup subsys cpuacct
Linux version 3.14.20 (root@puppypc22591) (gcc version 4.6.4 (Ubuntu/Linaro 4.6.4-6ubuntu2) ) #1 SMP Thu Jan 8 13:19:06 GMT 2015
e820: BIOS-provided physical RAM map:
BIOS-e820: [mem 0x0000000000000000-0x000000000009f3ff] usable
BIOS-e820: [mem 0x000000000009f400-0x000000000009ffff] reserved
BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
BIOS-e820: [mem 0x0000000000100000-0x00000000da87efff] usable
BIOS-e820: [mem 0x00000000da87f000-0x00000000db07ffff] reserved
BIOS-e820: [mem 0x00000000db080000-0x00000000df9befff] usable
BIOS-e820: [mem 0x00000000df9bf000-0x00000000dfabefff] reserved
BIOS-e820: [mem 0x00000000dfabf000-0x00000000dfbbefff] ACPI NVS
BIOS-e820: [mem 0x00000000dfbbf000-0x00000000dfbfefff] ACPI data
BIOS-e820: [mem 0x00000000dfbff000-0x00000000dfbfffff] usable
BIOS-e820: [mem 0x00000000dfc00000-0x00000000dfffffff] reserved
BIOS-e820: [mem 0x00000000f8000000-0x00000000fbffffff] reserved
BIOS-e820: [mem 0x00000000fec00000-0x00000000fec00fff] reserved
BIOS-e820: [mem 0x00000000fec10000-0x00000000fec10fff] reserved
BIOS-e820: [mem 0x00000000fed80000-0x00000000fed80fff] reserved
BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved
BIOS-e820: [mem 0x00000000ffc00000-0x00000000ffffffff] reserved
BIOS-e820: [mem 0x0000000100000000-0x0000000106ffffff] usable
BIOS-e820: [mem 0x0000000107000000-0x000000011effffff] reserved
Notice: NX (Execute Disable) protection cannot be enabled: non-PAE kernel!
SMBIOS 2.7 present.