triple head: xrandr commands ignored

[Alex Deucher]

On Fri, Apr 28, 2017 at 5:46 AM, Felix Miata <mrmazda at earthlink.net> 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:
> http://fm.no-ip.com/Tmp/Linux/Xorg/ATI3/xorg.0.log-tw-fi965-hd5450-atiDrv-viz-e
>
> 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.

Alex