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Re: Fw: Dropping i386 non-PAE as a supported kernel flavour in Precise Pangolin


Hi, I'm running Lubuntu on a non-PAE kernel too :)

1.4GHz Pentium M in a Dell Latitude D505 with 512MB RAM from 2004. It's my
main production machine and runs Lubuntu like a charm.

I've been reading through the emails and irc logs, and it sounds like the
kernel team is maintaining the non-pae kernel in Precise (but not beyond),
but just not setting it as the default -- any chance someone can convince
them to make the non-pae kernel the default in just Lubuntu? Colin Watson
mentioned this as a possibility in the Technical Board meeting [1].



On Sun, Nov 20, 2011 at 5:31 PM, Yorvyk <yorvik.ubunto@xxxxxxxxxxxxxx>wrote:

> On Sun, 20 Nov 2011 13:20:35 -0800
> Jonathan Marsden <jmarsden@xxxxxxxxxxx> wrote:
> > On 11/20/2011 07:29 AM, Chow Loong Jin wrote:
> >
> > > On 20/11/2011 19:31, Yorvyk wrote:
> >
> >
> > >> If a CPU can't support PAE it can't support more than 4GiB of RAM,
> > >> so the PAE part of the kernel shoudn't come into play.
> >
> >
> >
> > > From what I understand, PAE has a different set of paging structures
> > > compared to non-PAE. Does the kernel know to fall back onto non-PAE
> > > mode if it cannot enable PAE on a CPU?
> >
> >
> > Which way to do things is basically a compile time option for the
> > kernel, as I understand it.  So, if a PAE kernel is used, it can *only*
> > be run on processors that support the additional PAE instructions.  Even
> > if a machine only has 128MB RAM, it you try to run a PAE kernel on it,
> > and the CPU lacks the PAE instruction, it is not going to run.
> >
> > The real question is: are there really any CPUs in general purpose
> > desktops or laptops, in any significant quantity at all, that Ubuntu
> > 11.10 i386 kernels work on, which PAE kernels do not work on?
> >
> > Other than the early 400MHz Pentium-M, which are pretty rare, I don't
> > think anyone has seen such a CPU yet.  Via C3 and AMD Geode LX already
> > cannot run current Ubuntu 11.10 default kernels anyway.
> >
> Having trawled the net for info on this, I have no problem with dropping
> the non-PAE kernel as it appears to only effect a very,very, very small
> number of users.  Whether these are current or potential users is going to
> be very hard to find out, unless they start jumping up-and-down screaming.
> My one concern was the alleged overhead of the PAE kernel but, this
> appears, from the various benchmarks I've seen, to be trivial and probably
> unnoticeable in normal use.  I have installed PAE kernels on a couple of
> machines, one oneiric and one precise, and have not noticed any problems so
> far.
> I would imagine by the time 12.04 is no longer supported, 32 bit ubuntus
> may well be limited to the ARM anyway.
> --
> Yorvyk
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