Subject: Re: more infos about UVM
To: / IMAP - greensrv <>
From: David Laight <>
List: tech-kern
Date: 11/06/2006 19:52:20
On Mon, Nov 06, 2006 at 08:37:21PM +0100, / IMAP - greensrv wrote:
> Hi,
> Remember that in real mode some memory is used to prepare CPU to switch 
> into protected mode and to enable other stuff. Some memory is user also 
> for bios and for example "video memory". I guess this is the point, but 
> I could be wrong.

For a normal i386 system.

The kernel is certainly loaded to physical address 1MB.
Addresses from 640k to 1M are used for memory mapped IO (and the DRAM
probably doesn't get mapped elsewhere).

Some of the memory below 640k is used by the BIOS, and ACPI stuff
does involve bios calls...
I suspect that no attempt is made to use any nominally available
memory below 640k.


David Laight: