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[martinr <1307105@xxxxxxxxxxxxxxxxxx>]

I also ran into this problem with Xubuntu 16.04 LTS.
I'm running an Intel Pentium M 735, Dothan, (2MB L2 Cache, 1.70 GHz, 400 MHz FSB) (CPUID: 6.D.6 (hex) or 06D6h or 6.13.6 (dec)).

When I lookup the specification on the Intel site, then it says:
Physical Address Extensions (PAE) 32-bit is available.
(source: http://ark.intel.com/products/27588/Intel-Pentium-M-Processor-735-2M-Cache-1_70A-GHz-400-MHz-FSB#@specifications )

Are there any adverse effects known about the boot parameter "forcepae"?

What I need to know is if the compiled stock kernel / compiler implemented work-arounds for the W25 and W40 errata* to the Dothan (stepping B1) family of processors.
If that is so, then the PAE flag can be set / forced without problems.

* Intel Celeron M Specification Update errata
W25: Upper Four PAT Entries Not Usable with Mode B or Mode C Paging

W40: INIT Does Not Clear Global Entries in the TLB
Problem: INIT may not flush a TLB entry when:
1. The processor is in protected mode with paging enabled and the page global
enable flag is set (PGEbit of CR4 register)
2. G bit for the page table entry is set
3. TLB entry is present in TLB when INIT occurs
Implication: Software may encounter unexpected page fault or incorrect address
translation due to a TLB entry erroneously left in TLB after INIT.
Workaround: Write to CR3, CR4 (settingbits PSE, PGE or PAE) or CR0 (setting bits PG or PE)
registers before writing to memory early in BIOS code to clear all the global entries
from TLB.
(source: http://download.intel.com/support/processors/mobile/celeron/sb/30030336.pdf )

See also:
http://ubuntuforums.org/showthread.php?t=2326769&p=13499191#post13499191

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https://bugs.launchpad.net/bugs/1307105

Title:
  Kernel install fails due PAE checks

Status in linux package in Ubuntu:
  Triaged

Bug description:
  [TRIAGE NOTE]
  When a user boots Ubuntu Live/Install media with 'forcepae' option, the option should automatically be added to /etc/default/grub, or kernel upgrades will refuse to install when they do not see pae capability in cpuinfo.

  [ORIGINAL REPORT]
  On Thinkpad T42 with Pentium M processor linux image upgrade fails with message "This kernel does not support a non-PAE CPU.". System was installed from  ubuntu-14.04-beta2-desktop-i386.iso with "forcepae" kernel option. After install, system works, but cannot be upgraded to laters kernel.

      root@t42:/boot# apt-get upgrade
      Reading package lists... Done
      Building dependency tree
      Reading state information... Done
      You might want to run 'apt-get -f install' to correct these.
      The following packages have unmet dependencies:
       linux-image-extra-3.13.0-24-generic : Depends: linux-image-3.13.0-24-generic but it is not installed
       linux-image-generic : Depends: linux-image-3.13.0-24-generic but it is not installed
      E: Unmet dependencies. Try using -f.

      root@t42:/boot# apt-get install -f
      Reading package lists... Done
      Building dependency tree
      Reading state information... Done
      Correcting dependencies... Done
      The following extra packages will be installed:
        linux-image-3.13.0-24-generic
      Suggested packages:
        fdutils linux-doc-3.13.0 linux-source-3.13.0 linux-tools
      The following NEW packages will be installed:
        linux-image-3.13.0-24-generic
      0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
      3 not fully installed or removed.
      Need to get 0 B/14.6 MB of archives.
      After this operation, 32.3 MB of additional disk space will be used.
      Do you want to continue? [Y/n]
      (Reading database ... 196089 files and directories currently installed.)
      Preparing to unpack .../linux-image-3.13.0-24-generic_3.13.0-24.46_i386.deb ...
      This kernel does not support a non-PAE CPU.
      dpkg: error processing archive /var/cache/apt/archives/linux-image-3.13.0-24-generic_3.13.0-24.46_i386.deb (--unpack):
       subprocess new pre-installation script returned error exit status 1
      Examining /etc/kernel/postrm.d .
      run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.13.0-24-generic /boot/vmlinuz-3.13.0-24-generic
      run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.13.0-24-generic /boot/vmlinuz-3.13.0-24-generic
      Errors were encountered while processing:
       /var/cache/apt/archives/linux-image-3.13.0-24-generic_3.13.0-24.46_i386.deb
      E: Sub-process /usr/bin/dpkg returned an error code (1)

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