[SeaBIOS] [PATCH v2] x86emu: Correctly handle 0x66 prefix for some instructions

Julian Pidancet julian.pidancet at gmail.com
Mon Apr 2 11:42:07 CEST 2012

On Mon, Apr 2, 2012 at 6:51 AM, Michael Tokarev <mjt at tls.msk.ru> wrote:
> What is the outcome of this patch?  I mean, does it actually fix
> something visible, instead of a potential problem?

x86emu in it's current state is unable to emulate correctly 16bit code that
has been produced by GCC.
This patch is an attempt to fix it.
If this is what you want to know, no it doesn't fix something that has
already been reported as working. It just adds more correctness to the

> I asked another question related to xorg vesa driver, also related to
> qemu, about it being unable to find available resolutions when run under
> qemu -- this: http://lists.x.org/archives/xorg-devel/2012-March/030037.html
> Is this 0x66 issue related to my question somehow? :)

This question is vgabios specific. This patch concerns seabios VGA rom.
I believe the reason why Xorg can't use a resolution superior to 1024x768
is because vgabios doesn't implement the 15h VBE function, and therefore
doesn't expose a valid EDID block to Xorg. SeaBIOS VGA rom  suffers from
the exact same problem, and I already started a discussion on the mailing list
in order to fix it. Have a look at:
if you're interested.
Still, this is unrelated to what this patch tries to achieve.


More information about the SeaBIOS mailing list