David Coulson on 22 Dec 2008 16:23:07 -0800

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Re: [PLUG] swap on ram disk

LeRoy wrote:
> If you look at the kernel source you can set a 32 bit processor with the
> ability to access 64GB of ram under High memory support.
> Select this if you have a 32-bit processor and more than 4
> gigabytes of physical RAM.
Yep, that is PAE. However, if you have 4Gb of RAM, even with PAE, you're 
still going to lose a bunch to access other memory locations on the 
systems, plus you have a chuck of reserved memory for the address 
mapping used for PAE (Since it maps a 36bit address space onto your 
32bit address space - I think that eats up 128Mb on a 4Gb box, 256Mb on 
a 8Gb box and so forth - You lose a couple of Gigs just for PAE maps 
when you get to 64Gb).

PAE is a hack, and a nasty one at that. If your CPU supports 64bit, 
you're better off running an x86_64 kernel and running 32bit apps on it.
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