> Physical Address Extensions (PAE) 32-bit is available. If the pae flag is not present in /proc/cpuinfo then PAE is not enabled on your particular CPU, even if it is available for other CPUs in the same family. The CPU indicates PAE support (or not) in the result of the CPUID instruction, which is hardcoded in the processor microcode.
> Are there any adverse effects known about the boot parameter "forcepae"? I have not seen any reports of adverse effects, but given the small number of users and non-extensive testing it is possible. > If that is so, then the PAE flag can be set / forced without problems. afaik those errata would not be a problem as Linux does not use PAT on Pentium M, and the TLB is cleared on init. But there may be other issues or internal errata that Intel hasn't published. Nobody knows why Intel disabled PAE for these processors. As the docs say: forcepae [X86-32] Forcefully enable Physical Address Extension (PAE). Many Pentium M systems disable PAE but may have a functionally usable PAE implementation. Warning: use of this parameter will taint the kernel and may cause unknown problems. The CPU is run out-of-spec so there are no guarantees. If this is not acceptable then the next easiest workaround is to compile your own kernel with PAE disabled (CONFIG_X86_PAE=n). -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. 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) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1307105/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp