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SubjectRe: High Mem Options
Hi William,

Right, but if the pagetable pointing to a different 4GB subsets of memory.
The performance of the system can be disastrous, not?

Best regards,
Michael

On Wed, 5 Mar 2003 04:57:47 -0800
William Lee Irwin III <wli@holomorphy.com> wrote:

> On Wed, Mar 05, 2003 at 01:49:37PM +0100, Michael Vergoz wrote:
> > That i can't understand i when the system going to the protect mode.
> > How the system can use over 4GB memory ?
> > On freebsd, when you have over 4GB the system say "XGB of XGB skiped..."
> > (i'v got a machine with 8GB running on freebsd and without memory spare)
>
> The cpu can't look at more than 4GB at a time.
>
> Protected mode doesn't help this, turning paging on and PAE on does.
>
> What it can do is point pagetables at different 4GB subsets of memory.
>
> c.f. kmap_atomic() for how to window around using what's actually a
> very small set of PTE's.
>
>
> -- wli
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