On Wed, Apr 08, 2015 at 09:21:17PM -0700, Joseph Areeda wrote:
> 
> So I bought a new GTX960 which purports to support 4 monitors so I
> hooked up a third one but SL6 still only sees 2.
> 


In my experience, requirements for multi-monitor support are poorly
documented for most video cards.

For example, the ASUS Z87/Z97 mobo has 3 video outputs connected
to the on-CPU video. It is supposed to support 3 monitors,
but to actually make it work, I had to get down all the way to
data sheet for the on-CPU video controller where they explain
how due to a missing clock (3 clock sources needed, only 2 available),
all 3 monitors have to run at identical resolution and that
only some combinations of DVI and DisplayPort connections
are supported (3 DVI is okey, 2 DVI + 1 DP not okey, or some such
arcane rules).

In practice, it means that all 3 monitors have to be identical,
all connected with DVI-to-{HDMI,DP,miniDP} cables (passive adapters).

Maybe you have mismatched monitors and your particular combination
cannot be done by the hardware (and good luck finding the nvidia
documentation for this - intel seems to do better with public docs).

Again, in practice, if you have nvidia video card, install latest kmod-nvidia (from elrepo
or otherwise), run "nvidia-settings" and your monitors do not show up,
you are toast.

(Some vendors are upfront with these problems - ASUS AMD socket AM1 mobo
plainly states - 3 video outputs - VGA, DVI, HDMI - but only 2 monitors
can be connected).


K.O.


>
> I still have some debugery to do but I wanted to ask if anyone has
> gotten more than 2 monitors to work on one video card?
> 
> That will help direct my efforts.
> 
> For the record the output of nvidia-smi looks like:
> 
>    +------------------------------------------------------+
>    | NVIDIA-SMI 346.59     Driver Version: 346.59 |
>    |-------------------------------+----------------------+----------------------+
>    | GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile
>    Uncorr. ECC |
>    | Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util
> Compute M. |
>    |===============================+======================+======================|
>    |   0  GeForce GTX 960     Off  | 0000:01:00.0     N/A
>    |                  N/A |
>    |  0%   46C    P8    N/A /  N/A |    370MiB /  2047MiB | N/A
> Default |
>    +-------------------------------+----------------------+----------------------+
> 
>    +-----------------------------------------------------------------------------+
>    | Processes: GPU Memory |
>    |  GPU       PID  Type  Process name
> Usage      |
>    |=============================================================================|
>    |    0            C+G   Not
>    Supported                                         |
>    +-----------------------------------------------------------------------------+
> 
> 
> thanks,
> Joe
> 

-- 
Konstantin Olchanski
Data Acquisition Systems: The Bytes Must Flow!
Email: olchansk-at-triumf-dot-ca
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