[Dri-devel] Re: AMD x86-64

[Mike A. H. <mh...@re...>]

On Wed, 12 Mar 2003, Jon Smirl wrote:

>http://arstechnica.com/cpu/03q1/x86-64/x86-64-1.html
>
>When AMD's engineers started looking for legacy x86 features to
>jettison, the first thing to go was the segmented memory model.
>Programs written to the x86-64 ISA will use a flat, 64-bit
>virtual address space. Furthermore, legacy x86 applications
>running in long mode's compatibility sub-mode must run in
>protected mode. Support for real mode and virtual-8086 mode are
>absent in long mode and available only in legacy mode. This
>isn't too much of a hassle, though, since, except for a few
>fairly old legacy applications, modern x86 apps use protected
>mode.
-----------------------------------------------------
>
>So if the x86-64 is getting rid of real mode when
>running a 64b OS, how is XFree going to make those
>nasty old vm86 INT 10 calls for things like getting
>DDC and resetting secondary adapters?

Simple.  x86emu is an x86 compatible software emulator which is 
included in XFree86 source code and is used for booting x86 BIOSs 
and whatnot on non-x86 architectures such as Alpha, PPC, etc.

When the AMD x86_64 is running in the 64bit mode, XFree86 uses 
x86emu to power up the video BIOS.  int10 works good enough that 
you don't even know it's being done via CPU emulation.  ;o)

Hope this helps.
TTYL


-- 
Mike A. Harris     ftp://people.redhat.com/mharris
OS Systems Engineer - XFree86 maintainer - Red Hat