Can't use third monitor, Radeon HD 8830M

[Eino Virtanen]

Hello Alex,

Thank you, you saved my day!! Your advice solved the problem.


Best regards,
E

--
Sent from mobile. Please excuse any typos.

On Tue, Sep 11, 2018, 20:49 Alex Deucher <alexdeucher at gmail.com> wrote:

> On Tue, Sep 11, 2018 at 12:24 PM Eino Virtanen <eino.vir at gmail.com> wrote:
> >
> > Hello everyone,
> >
> > I have three monitors. Each connected with DVI cables to a Radeon HD
> > 8830M. Two of them are connected with a DVI-DP adapter. The problem is
> > that I can only enable two of the monitors simultaneously, otherwise I
> > get this error message: "xrandr: Configure crtc 0 failed"
>
> Are you using active or passive DVI->DP adapters?  Are all of the
> displays on a single GPU?  Your GPU only has two PLLs for non-DP
> displays, so it can only drive two independent sets if display timing.
> If you want to use more than 2 non-DP monitors, you need to use the
> exact same modeline on at least two of them.  All of the modes you are
> trying to set have different timings, so it's not possible:
>
>   1680x1050 (0x81) 146.250MHz -HSync +VSync +preferred
>         h: width  1680 start 1784 end 1960 total 2240 skew    0 clock
> 65.29KHz
>         v: height 1050 start 1053 end 1059 total 1089           clock
> 59.95Hz
>
>   1920x1200 (0x8c) 154.000MHz +HSync -VSync *current +preferred
>         h: width  1920 start 1968 end 2000 total 2080 skew    0 clock
> 74.04KHz
>         v: height 1200 start 1203 end 1209 total 1235           clock
> 59.95Hz
>
>   1680x1050 (0x8f) 119.000MHz +HSync -VSync *current +preferred
>         h: width  1680 start 1728 end 1760 total 1840 skew    0 clock
> 64.67KHz
>         v: height 1050 start 1053 end 1059 total 1080           clock
> 59.88Hz
>
> Try either selecting a modeline that is common across at least two of
> the displays, or use randr to add one of the 1680x1050 modelines to
> the other connector and hope that the monitor will support it.
>
> Alex
>
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