Announcement

Collapse
No announcement yet.

Concerns Over No PAE Kernel In Ubuntu 12.04 LTS

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    uh, ok... i just checked the performance concern.
    there seems to be no penalty for using PAE Kernel, as far as the last benchmarks for PAE kernels were concerned. i just hope it does apply for my system aswell...

    Comment


    • #17
      Originally posted by rapsure View Post
      Well that mean that a lot of Pentium M laptops will not work with Ubuntu too. I tried to use PAE on all of the i686 instruction set computers and that didn't workout. Turns out that several generations of the Pentium M does not support PAE at all.
      Pentium M does not support PAE because they are not 64 bit CPUs. In fact both Pentium M (I had a Dothan as my first laptop CPU) are 32 bit as the next iteration (Pentium Core or "Core1") do not support 64 bit or PAE.

      Comment


      • #18
        Originally posted by ciplogic View Post
        Pentium M does not support PAE because they are not 64 bit CPUs. In fact both Pentium M (I had a Dothan as my first laptop CPU) are 32 bit as the next iteration (Pentium Core or "Core1") do not support 64 bit or PAE.
        PAE has nothing to do with 64bit support. PAE has been around from before AMD64 was ever conceived.

        Comment


        • #19
          Originally posted by ciplogic View Post
          Pentium M does not support PAE because they are not 64 bit CPUs. In fact both Pentium M (I had a Dothan as my first laptop CPU) are 32 bit as the next iteration (Pentium Core or "Core1") do not support 64 bit or PAE.
          If that were the case, then they would be advocating dropping ALL support for 32bit altogether, and forcing 64bit down everyone's throat. As it happens, I have a 32bit intel tablet that does support PAE, so THAT incorrect assumption of yours would force me right out of ubuntu altogether (assuming that I used it, which I don't...)

          Note that this dropping support for older hardware does happen over time. First the major distros dropped support for i386 (i.e. 80386 chips rather than the use as a general way of saying "32bit"), then i486, then i586 (I actually had an interesting glitch with this... apparently K6's -- including II and III -- are missing a couple of features that are required for "full" compatibility with i686, so an i686 kernel won't run on them), now its time to drop non-PAE. IMO, it is a natural and necessary progression.

          Fortunately, there isn't much risk of 32bit PAE being dropped any time soon, since this hardware is still being manufactured and advanced.

          Comment


          • #20
            Originally posted by jakubo View Post
            "drop support for the non-PAE 32-bit Linux kernel"

            im somehow getting the impression that either i or others understand this wrong.

            Isnt it about dropping support for Non-PAE-Kernels?
            Yes; the article title is incorrect.

            which means, that if you are running a pentium M it probably wont work, as the hardware doesnt support that feature?
            Yes.

            maybe it would work, but as far as i remember the PAE kernel wasnt performing very well...
            Trying to boot a PAE kernel on hardware that doesn't support PAE leads to an instant kernel panic. Been there, done that.

            maybe a poll to find out how many people using 32bit systems actually have more than 3,4 GB Ram, which i recall to be the physical limit of adresses on 32 bit, would be in order...
            The amount of RAM installed doesn't matter. If the CPU doesn't support PAE, you can't use a PAE kernel no matter what amount of memory is installed.

            As an aside, the I suspect the real reason for Ubuntu wanting to get rid of the non-PAE kernel is that PAE kernels support NX, which is nice for improved security (you can emulate it, but that has downsides).

            Comment


            • #21
              When U drops PAE kernels it increases the work for other distributions which use U kernels (with small mods only). It is certainly correct that mainly the older Pentium M chips are affected, but those are definitely not slower than current Atom cpus. There is basically no need to upgrade those systems when you dont want to do more than surfing the web or writing some letters. But when you can not even install a current distro it is not fun. In the case you use more than 3 gb ram on a system which can handle not user 64 bit but pae you can always install that kernel later, should not be problematic. When you compare the kernel configs the non-pae and pae one those are very similar, so you can derive one from the other. It is definitely no huge problem to maintain two 32 bit kernels. I understand that there is no need for the 64 bit server flavour, i never complied that anyway but there should be a non-pae kernel für 32 bit systems by default. I personally think that most ppl who have got more than 3 gb ram have got already a 64 bit cpu, so in theory you could more easyly drop the pae kernel - that would affect less users...

              Comment


              • #22
                ciplogic: PAE is a technology to get 4+ GB of RAM on a system without having to switch to 64-bit.
                Pentium M Dothan CPU's with a 533MHz FSB support PAE very well. The "NX bit" security feature introduced on this revision of Dothan relies on PAE. Pentium M Banias, and Dothans with 400MHz FSB, didn't yet have NX bit so also don't need a proper PAE implementation as much - laptops from that time often still had 512MB of RAM, sometimes even 256, and nobody even cared about having more than 2GB. Many chipsets for laptops also didn't support over 2GB of RAM.

                Isn't there a way to detect if there's a Pentium M CPU and then disable PAE?
                Last edited by AlbertP; 11-10-2011, 09:41 AM.

                Comment


                • #23
                  When you compile a kernel with pae then there is no way to disable that. Then you need a cpu that has support for this. Similar to a 64 bit kernel that can not run on 32 bit.

                  Comment


                  • #24
                    Originally posted by gremble View Post
                    PAE kernels do not run on non-PAE machines. Been bitten by this before. This is stated clearly in the article.
                    Is this a figment of your imagination? Because I can easily run PAE enabled kernels (Fedora i686 has had them for years) on pre PAE hardware and CPUs.

                    Comment


                    • #25
                      Maybe the pae kernel is installed on supported systems when you install it (just like U does). But on a live system it is impossible. It should be easy to verify with vbox without pae. If you have got a cpu that has got no output with

                      grep -o pae /proc/cpuinfo

                      then you can try it too.

                      Comment


                      • #26
                        That is wrong, automatic choosing of PAE/non-PAE kernel also works on live media with syslinux ifcpu64.c32 module.

                        Comment


                        • #27
                          Originally posted by birdie View Post
                          Is this a figment of your imagination? Because I can easily run PAE enabled kernels (Fedora i686 has had them for years) on pre PAE hardware and CPUs.
                          Nope, not a figment at all

                          http://sazwqa.wordpress.com/2008/06/...on-virtualbox/

                          https://bugs.launchpad.net/ubuntu/+s...ux/+bug/201089

                          Comment


                          • #28
                            Does no one else think the title of the news post is misleading for link clicks?

                            "Concerns Over No PAE Kernel"

                            When the discussion about no non-pae kernel? Not no pae kernel...

                            Comment


                            • #29
                              @chithanh

                              interesting aspect, but that requires that there EXISTS a kernel, but U wants to drop the kernel completely.

                              Comment


                              • #30
                                OMG, which idiots running Ubuntu on Pentium II or VIA C3? OMG, ppl are weird ...

                                Comment

                                Working...
                                X