Re: Intel 875 Motherboard cant use 4GB of Memory.

[Richard B. Johnson]

On Wed, 2 Jun 2004 reg@xxxxxxx wrote:

> >
> > Wrong.  Ever since the Pentium Pro, x86 processors have had 36-bit
> > *physical* addressing.  This is why PAE-mode paging was introduced.  A
> > sane BIOS would configure the memory controller to remap some of the
> > memory above 4G physical to allow for memory mapped devices.  It sounds
> > like this board's BIOS isn't doing that, or at least not reporting it in
> > the e820 map.
> >
> Hummm.
>
> Let me restate the fact that I dont understand how PC hardware works, but
> I can understand how the area for PCI devices has to come out of the
> KERNEL address space, but why does it have to be subtracted from the USER
> address space too?
>
>
> --
>                                         Reg.Clemens
>                                         reg@xxxxxxx


It isn't. However some of the user address-space is used by the kernel
so a user can't address 32 bits of (data) space either. The sum of
the address-spaces that each user can access can far exceed all the
RAM and certainly 32-bits of space. That's why we have swap-files.


Cheers,
Dick Johnson
Penguin : Linux version 2.4.26 on an i686 machine (5570.56 BogoMips).
            Note 96.31% of all statistics are fiction.


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