[sf-lug] sf-lug Digest, Vol 62, Issue 26

Akkana Peck akkana at shallowsky.com
Mon Mar 28 19:16:07 PDT 2011

Alison Chaiken writes:
> Akkana writes:
> >On Ubuntu, you'll only see 3G RAM with the standard kernel; to see
> >all of it, install the PAE kernel, package linux-image-generic-pae.
> >I'm not clear why PAE isn't the default.
> I thought PAE was a kernel-level default install?   And that x86_64

It's an alternate kernel: PAE is an option when you build the kernel.

> didn't need it anyway?    Akkana, are you installing the PAE package
> on a 32-bit machine?

I believe that's correct, that it only matters on 32-bit systems.

> On Fedora, "yum list all \*pae\*" and (\*PAE\*) lists nothing.
> I guess since PAE requires an additional level of address translation
> that it could degrade performance in situations where memory usage
> never exceeded 3 GB and swap was rarely used.    Are there such
> desktop systems any more though?

It's true that I very seldom get close to using 3G, let alone 4.
But I like knowing that RAM is available if I ever want it.
Perhaps I'm just being silly.

There is supposed to be a slight performance hit from using PAE.
I've never tried to measure the difference.


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