Multiseat with VGAArbiter on 2 Radeon cards

Steffen Schaumburg steffen at
Tue Dec 22 08:45:38 PST 2009

Okay I tried turning off arbiter by just editing .config
("CONFIG_VGA_ARB=n") but when I type my usual "make && make
modules_install" it changes it back automatically. I tried rebooting
into this new kernel anyways but it continues to load arbiter as
evidenced in the boot messages and as expected it still doesn't work. I
haven't been able to turn off arbiter in make menuconfig as its
automatically turned on by other options so it doesn't even show up in

Does anyone have any ideas what I'm doing? Or is anyone out here running
a multiseat setup with radeon cards? I'd be very very grateful if you
could send me your xorg.conf, ?dm config (e.g.
/usr/share/config/kdm/kdmrc), the version numbers of your xorg-server,
type&version of driver (at this stage I'd even try the proprietary
drivers) and what you use to launch X as well as its version.

So any tips, no matter how unlikely you think they are to work, would be
greatly appreciated.


> Okay I figured I might as well try Tiago's idea. I'm not sure what if I
> used the right command but here's what I tried:
> xterm -display :1 -e bash &
> xterm -display :1.0 -e bash &
> xterm -display localhost:1 -e bash &
> xterm -display localhost:1.0 -e bash &
> I tried all four as both root and user and they all fail saying "Can't
> open display: localhost:1.0" (with different display depending on what I
> used).
> Thanks, Steffen
> Steffen Schaumburg wrote:
>> Hi,
>> thanks both of you for your replies - I'm going to try the KMS method
>> first. Now the problem is I can't turn off Arbiter in the kernel, make
>> menuconfig can find it with the search, but the option isn't in the
>> menu. Is there a boot option to force off arbiter (or, alternatively, to
>> force on KMS which would turn off arbiter by necessity?)? I checked the
>> docs at
>> but can't see anything. Or should I just manually edit the .config file
>> - I'm inclined to trust menuconfig to not be displaying the option for a
>> reason, or am I giving it too much credit? Any pointers would be
>> appreciated.
>> Thanks, Steffen
>>> Multicard and multiseat for radeon doesn't need vgaarb; use KMS
>>> instead and your cards will both come up at boot.
>>> Posting from a mobile, pardon my terseness. ~ C.
>>>> On Dec 5, 2009 9:30 AM, "Tiago Vignatti" <tiago.vignatti at
>>>> <mailto:tiago.vignatti at>> wrote:
>>>> On Fri, Dec 04, 2009 at 09:00:19PM +0100, ext Steffen Schaumburg
>>>> wrote: > Hi everyone, > I'm trying ...
>>>> yes. And the log says you're indeed using it.
>>>>> The current status of my work is: > >From pressing the power button
>>>> to kdm loading it displays i...
>>>> humm, seems not issue with vga arbitration. I'd guess maybe missed mode
>>>> setting. Try to start an app on the monitor black and see if
>>>> connects. If this
>>>> succeeds then the arbiter is doing its job okay.  

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