Re: PAE (was: Debian Gnome Or XFCE ?)
On Mon, 24 Aug 2015 13:52:30 -0400 (EDT), Mirko Parthey wrote:
>
> On Mon, Aug 24, 2015 at 06:45:10AM -0400, Stephen Powell wrote:
>> Furtherfore, a non-PAE kernel is
>> useful even on PAE-capable hardware. The main purpose of PAE is to
>> address memory above 4G. But if the machine has less than 4G of
>> memory, what does a PAE-capable kernel buy you? PAE-capable kernels
>> tend to be a bit bigger, all other things being equal, than non-PAE
>> kernels, which chews up more precious memory with no obvious benefit.
>
> One such benefit is that the NX bit (non-executable memory pages)
> is only available with 64 bit page table entries, which in turn depend on
> PAE mode. This could be an argument for preferring a PAE kernel on
> PAE-capable hardware.
Wow, did I really say, "Furtherfore"? Mercy! I need to do a better job
of proofreading. Obviously, that was supposed to be "Furthermore".
Anyway, to your point:
PAE may be a necessary condition for NX, but it is not a sufficient condition.
I am presently using three 32-bit computers: one is a Pentium M (2G), one is
a Pentium 4 (2G), and one is a Xeon (4G). All three are PAE-capable, and all
three are presently running PAE Linux kernels. And all three display the
following message during boot, according to "dmesg|less":
Notice: NX (Execute Disable) protection missing in CPU!
So, for my hardware, that argument doesn't seem to hold up. Am I missing
something?
--
.''`. Stephen Powell <zlinuxman@wowway.com>
: :' :
`. `'`
`-
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