triple head: xrandr commands ignored

Michel Dänzer michel at
Sat Apr 29 01:55:01 UTC 2017

On 29/04/17 04:15 AM, Alex Deucher wrote:
> On Fri, Apr 28, 2017 at 5:46 AM, Felix Miata <mrmazda at> wrote:
>> Felix Miata composed on 2017-04-28 05:22 (UTC-0400):
>>> Felix Miata composed on 2017-04-27 06:35 (UTC-0400):
>>>> openSUSE Tumbleweed
>>>> kernel 4.10.10
>>>> server 1.19.3
>>>> ATI HD5450 PCIe gfxcard (Cedar)
>> ...
>> When I use this startup script:
>> xrandr --output DVI-0 --primary --mode 1920x1200 --left-of HDMI-0
>> xrandr --output HDMI-0 --mode 1920x1080
>> xrandr --output VGA-0 --mode 1680x1050 --above DVI-0
>> xrandr --dpi 108
>> things improve dramatically. 1920x1080 appears right of 1920x1200, and mouse can
>> reach them both, but 1680x1050 remains asleep.
>> Xrandr and Xorg.0.log combined:
>> Is this low-budget Sapphire ATI Cedar gfxcard not supposed to be able to produce
>> on all three outputs at once?
> All evergreen cards only have 2 PLLs so that means they can only
> support two independent clocks.  If you want to use more than two
> displays, you'll need to use displayport or for non-displayport, at
> least two of the displays need to be using the exact same display
> timing.

BTW, does only the pixel clock need to be identical, or do the
vertical/horizontal blanking periods also need to happen at the same time?

Earthling Michel Dänzer               |     
Libre software enthusiast             |             Mesa and X developer

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