F11: X starts at wrong resolution

Fulko Hew fulko.hew at gmail.com
Tue Feb 24 16:31:55 UTC 2009


On Tue, Feb 24, 2009 at 11:18 AM, Adam Jackson <ajax at redhat.com> wrote:

> On Tue, 2009-02-24 at 10:02 -0500, Fulko Hew wrote:
>
>
> > I've been curious about dual-headed operation for some time now,
> > and either because I'm using old software, or my hardware doesn't
> > support it, I've never been able to get it to work.  It could also
> > be because I don't know, or can't properly perform the correct
> > magic incantations.
> >
> > But the first question is always:
> > 'How can I tell if my hardware is capable of dual-headed operation'?
>
> If it's an intel chip, or a radeon chip, or an nvidia chip newer than a
> geforce 7 series, then it is dual-head capable.  nvidia chips should get
> even more support as we move to nouveau.
>
> There may be _limitations_ on how dualhead you can be.  For example:
>
> > 00:02.0 VGA compatible controller: Intel Corporation Mobile
> >         945GM/GMS, 943/940GML Express Integrated Graphics
> >         Controller (rev 03)
>
> Intel 915 and 945 series chips have a coordinate limit at 2048 pixels
> wide.  This manifests in ugly ways, but the short answer is that if
> you're trying to do something wider than that (like two 1280x1024
> displays next to each other) then it's not going to work right.  That's
> partly a hardware limit, and partly a software limit that's really hard
> to fix.


So if I read you right...  Since I have a 1600x1050 LCD display...
and there is a 2048 limit, then my 2nd display could only be 448 pixels
wide?  ;-(

I would have expected dual-head to imply (given the 2048 restriction)
that I could have two displays up to 2048 wide.  ie.  an internal display
at 1600x1050 and an external display at 1280x1024 (for example)

Right now, I haven't figured out a way to get the VGA connector to emit
'different' data than whats on the LCD.


> We also still don't do memory management as well as we ought to, which
> means you may need to explicitly set the Virtual size to allocate in the
> config file to get the size you want.


Forgive my ignorance, but why should I care about 'virtual size'?
I thought 'virtual size' simply allowed the 'physical screen' to scroll
around
on the 'virtual screen'.  Or does it mean that I need a 'really big' virtual
screen that has two physical screens consuming parts of that 'virtual
screen'?
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