Question about driver capatibilities - triple monitor?

Question about driver capatibilities - triple monitor?

[Csillag]

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Hi,

I am deciding the components on a new computer, and one of the most
important requirements is to have support for three monitors, under
GNU/Linux, with open-source drivers.

I know I can do this with AMD Eyefinity, but now I am trying to build an
Intel-based system.

So, can I do this with the Intel HD 4000 system, and the current
open-source graphics drivers?

Until so far, I thought that even though running 3 displays is supported by
HD4000, to really use this, two of the monitors has to be connected via
DisplayPort. ( See this FAQ:
http://www.intel.com/support/graphics/intelhdgraphics4000_2500/sb/CS-033714.htm)

Unfortunately, I could not find any LGA1155 motherboards that have more
than one DisplayPort outputs.

But now, thanks to GIGABYTE's PR about Thunderbolt and 4K (
http://www.gigabyte.com/MicroSite/323/4k.html ), I realized that it might
be possible to use a "DisplayPort to Dual-DisplayPort Adapter" to split a
DisplayPort 1.1 output into two channels, and drive two monitors from
there. (Of course the resolution is limited, but 1920 x 1200 is just what I
need.)

And then using a second port (DVI or HDMI), I could add the third monitor.

Is this supported by the hardware? (I mean on motherboards with Intel
7-series chipsets, and with DisplayPort outputs.) Is this supported by the
software?

Thank you for explaining:

    Kristof Csillag

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Re: Question about driver capatibilities - triple monitor?

[Ian Pilcher]

On 01/21/2013 06:05 PM, Csillag wrote:
> But now, thanks to GIGABYTE's PR about Thunderbolt and 4K (
> http://www.gigabyte.com/MicroSite/323/4k.html ), I realized that it
> might be possible to use a "DisplayPort to Dual-DisplayPort Adapter" to
> split a DisplayPort 1.1 output into two channels, and drive two monitors
> from there. (Of course the resolution is limited, but 1920 x 1200 is
> just what I need.)

Be careful.  When I looked into those "splitters", I found out that
they are closer to "federators".  In other words, they take 2 displays
and make them looks like 1 giant display to the operating system.

So 2 1920x1200 displays would appear to be a single 3840x1200 display.

This will give you the number of pixels that you expect, but your
desktop environment is unlikely to play all that well with such a
configuration.

(If anyone knows of a device that doesn't operate this way, please let
me know.  I'll almost certainly buy a couple.)

-- 
========================================================================
Ian Pilcher                                         arequipeno@gmail.com
Sometimes there's nothing left to do but crash and burn...or die trying.
========================================================================

Re: Question about driver capatibilities - triple monitor?

[Daniel Vetter]

On Tue, Jan 22, 2013 at 7:36 AM, Ian Pilcher <arequipeno@gmail.com> wrote:
> On 01/21/2013 06:05 PM, Csillag wrote:
>> But now, thanks to GIGABYTE's PR about Thunderbolt and 4K (
>> http://www.gigabyte.com/MicroSite/323/4k.html ), I realized that it
>> might be possible to use a "DisplayPort to Dual-DisplayPort Adapter" to
>> split a DisplayPort 1.1 output into two channels, and drive two monitors
>> from there. (Of course the resolution is limited, but 1920 x 1200 is
>> just what I need.)
>
> Be careful.  When I looked into those "splitters", I found out that
> they are closer to "federators".  In other words, they take 2 displays
> and make them looks like 1 giant display to the operating system.
>
> So 2 1920x1200 displays would appear to be a single 3840x1200 display.
>
> This will give you the number of pixels that you expect, but your
> desktop environment is unlikely to play all that well with such a
> configuration.
>
> (If anyone knows of a device that doesn't operate this way, please let
> me know.  I'll almost certainly buy a couple.)

Multistream display port should make this possible, though currently
no Intel hw supports it (nor any other open-source driver fwiws) :(

For your 3 monitor required a decen ivb based board should be good
enough, as long as you keep the restriction in mind that 2 of them
need to have the same dotclock (which in practice boils down to either
2x DP monitors or 2x identical monitors with the same type of
connector).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: Question about driver capatibilities - triple monitor?

["Kristóf, Csillag"]

At 2013-01-22 09:43, Daniel Vetter wrote:
> For your 3 monitor required a decen ivb based board should be good
> enough, as long as you keep the restriction in mind that 2 of them
> need to have the same dotclock (which in practice boils down to either
> 2x DP monitors or 2x identical monitors with the same type of
> connector).
> -Daniel
I'm still not clear on the details how to achieve this.

1. Option 1: "2x DP monitors"

How do I connect 2x DP monitors?

1a) I can not find any motherboards with more than one display port. Can 
you?

1b) Or do you mean using Thunderbolt instead one of the DisplayPort ports?

In this case I need 1 Thunderbolt + 1 DisplayPort + 1 Something else?

The only motherboard I know of with this configuration is the ASUS 
P8Z77-V Premium - which costs ~ 550 USD.
Can you recommend any other?

1c) Or do you mean using 2x (Thunderbolt -> Displayport) + something else.

I know about 2 dual-thunderbolt motherboards, all by GIGABYTE: 
GA-Z77X-UP4 TH,  GA-Z77X-UP5 TH, GA-Z77MX-D3H TH.

Did you mean these?

1c) Or do you mean achieving 2 DP by splitting a DP with a splitter like 
I mentioned?

Does this mean that any mobo with a DP should work? Take for example the 
Intel DQ77KB thin Mini-ITX board.
Can I split the DP into 2, and then connect 2 monitors via them, and add 
a third one with HDMI?

Option 2: "2x identical monitors with the same type of connector"

What does "identical monitor" mean here? Is same resolution/freq enough, 
or do we really need the same model?

For example, consider any of the GIGABYTE GA-B75N, GA-H77N-WIFI, 
GA-Z77N-WIFI models.They all have 2 HDMI + 1 DVI output.
Does that mean that if I connect two identical monitors to the HDMI 
ports, and a different one on the DVI port, and it should just work?

    * * *

Sorry for being persistent; I would really like to understand my options 
here.
(I intend to make a purchase based on the information, and I really 
can't afford to be wrong...)

Thank you:

    Kristof

Re: Question about driver capatibilities - triple monitor?

[Daniel Vetter]

tbh I have no idea whether you can actually by hw which supports 2x DP
out, it's certainly no common. The description was only from the hw
pov. It might be that the 2x thunderbolt works, otoh I've never tested
thunderbolt so I have no idea how well (or if at all) the pcie + dp
muxing works with our driver. Maybe the easiest way is to shoot for a
board with 2x HDMI or DP in total, since you can always use a passive
HDMI->DP dongle to drive the DP port in HDMI mode. But even just
finding boards with 3x digital output seems to be hard.
-Daniel

On Wed, Jan 23, 2013 at 12:46 PM, "Kristóf, Csillag"
<csillag.kristof@gmail.com> wrote:
> At 2013-01-22 09:43, Daniel Vetter wrote:
>>
>> For your 3 monitor required a decen ivb based board should be good
>> enough, as long as you keep the restriction in mind that 2 of them
>> need to have the same dotclock (which in practice boils down to either
>> 2x DP monitors or 2x identical monitors with the same type of
>> connector).
>> -Daniel
>
> I'm still not clear on the details how to achieve this.
>
> 1. Option 1: "2x DP monitors"
>
> How do I connect 2x DP monitors?
>
> 1a) I can not find any motherboards with more than one display port. Can
> you?
>
> 1b) Or do you mean using Thunderbolt instead one of the DisplayPort ports?
>
>
> In this case I need 1 Thunderbolt + 1 DisplayPort + 1 Something else?
>
> The only motherboard I know of with this configuration is the ASUS P8Z77-V
> Premium - which costs ~ 550 USD.
> Can you recommend any other?
>
> 1c) Or do you mean using 2x (Thunderbolt -> Displayport) + something else.
>
> I know about 2 dual-thunderbolt motherboards, all by GIGABYTE: GA-Z77X-UP4
> TH,  GA-Z77X-UP5 TH, GA-Z77MX-D3H TH.
>
> Did you mean these?
>
>
> 1c) Or do you mean achieving 2 DP by splitting a DP with a splitter like I
> mentioned?
>
> Does this mean that any mobo with a DP should work? Take for example the
> Intel DQ77KB thin Mini-ITX board.
> Can I split the DP into 2, and then connect 2 monitors via them, and add a
> third one with HDMI?
>
> Option 2: "2x identical monitors with the same type of connector"
>
> What does "identical monitor" mean here? Is same resolution/freq enough, or
> do we really need the same model?
>
> For example, consider any of the GIGABYTE GA-B75N, GA-H77N-WIFI,
> GA-Z77N-WIFI models.They all have 2 HDMI + 1 DVI output.
> Does that mean that if I connect two identical monitors to the HDMI ports,
> and a different one on the DVI port, and it should just work?
>
>    * * *
>
> Sorry for being persistent; I would really like to understand my options
> here.
>
> (I intend to make a purchase based on the information, and I really can't
> afford to be wrong...)
>
> Thank you:
>
>    Kristof
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Monitors on thunderbolt? (Was: Question about driver capatibilities - triple monitor?)

["Kristóf, Csillag"]

At 2013-01-23 13:02, Daniel Vetter wrote:
> tbh I have no idea whether you can actually by hw which supports 2x DP
> out, it's certainly no common. The description was only from the hw
> pov. It might be that the 2x thunderbolt works, otoh I've never tested
> thunderbolt so I have no idea how well (or if at all) the pcie + dp
> muxing works with our driver.
These DP splitters don't use any thunderbolt features, so the 
thunderbolt ports are only used as "simple" DisplayPort ports in these 
cases. So no actual PCIe transmission in muxed.
Still, it would be great if somebody could verify that Thunderbolt ports 
work (with the full SW stack) just as well as normal DisplayPort ports do.

Thank you:

     Kristof

Re: Question about driver capatibilities - triple monitor?

["Kristóf, Csillag"]

At 2013-01-23 13:02, Daniel Vetter wrote:
>   Maybe the easiest way is to shoot for a
> board with 2x HDMI or DP in total, since you can always use a passive
> HDMI->DP dongle to drive the DP port in HDMI mode. But even just
> finding boards with 3x digital output seems to be hard.
So, just to make sure that I get it right (before I actually start 
buying stuff): if I
- get a board like the Intel DH77DF, which has DP+HDMI+DVI, and
- connect 2 identical monitors to the DP and the HDMI ports, and
- connect a 3rd monitor to the DVI port,

then it's supposed to give me a desktop spanning 3 monitors?

I am using DVI monitors, so I guess I will need a passive DP -> DVI 
adapter and a passive HDMI -> DVI adapter.
Is that right?

Thank you for explaining:

    Kristof

Re: Question about driver capatibilities - triple monitor?

["Kristóf, Csillag"]

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At 2013-01-22 07:36, Ian Pilcher wrote:
> On 01/21/2013 06:05 PM, Csillag wrote:
>> But now, thanks to GIGABYTE's PR about Thunderbolt and 4K (
>> http://www.gigabyte.com/MicroSite/323/4k.html ), I realized that it
>> might be possible to use a "DisplayPort to Dual-DisplayPort Adapter" to
>> split a DisplayPort 1.1 output into two channels, and drive two monitors
>> from there. (Of course the resolution is limited, but 1920 x 1200 is
>> just what I need.)
> Be careful.  When I looked into those "splitters", I found out that
> they are closer to "federators".  In other words, they take 2 displays
> and make them looks like 1 giant display to the operating system.
>
> So 2 1920x1200 displays would appear to be a single 3840x1200 display.
>
> This will give you the number of pixels that you expect, but your
> desktop environment is unlikely to play all that well with such a
> configuration.

That's not necessarily a problem.

I had good results with the fakeXinerama library earlier.
You divert Xorg's Xinerama library with this library, feed it a text 
config file, describing what you want,
and then all X client applications that ask about the monitor layout 
(like window managers) get this data.

With this, one can make any big monitor appear like several devices. 
(And then you can maximize windows to the separated areas, etc.)

Of course you won't be able to use xrandr to configure the layout of the 
devices, but if all you want is one constant resolution, and the devices 
are placed in the proper order & orientation, this should not be a problem.

    * * *

I am more worried about the internals of this "federating" implementation.
Do I have to connect identical monitors, or identical resolution & 
frequency is enough?
(For example, would two different Samsung 1920x1200 @ 60 displays work?)

> (If anyone knows of a device that doesn't operate this way, please let
> me know.  I'll almost certainly buy a couple.)
+1

    Kristof


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