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Thread: Intel HD 4000 and three monitors

  1. #11
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    Mar 2013
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    Lightbulb There is a working patch

    Just a follow up, if somebody else stumble upon this. There is a small working patch (actually a revert)
    https://bugs.freedesktop.org/show_bug.cgi?id=62564

  2. #12
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    Apr 2013
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    Default working config with DVI+HDMI+DP (active DP2DVI adapter)

    Hi all,
    just as an info: as of today I have a working three monitor configuration as follows:

    Mainboard: Sapphire Pure Platinum H67 IPC-CI7S10H67 (MiniITX)
    CPU: Celeron G1610
    OS: Ubuntu 12.04 LTS

    left monitor: IBM L200p@1600x1200 via DVI
    center monitor: HannSpree ST281MAB@1920x1200 via HDMI
    right monitor: NEC 2070NX@1600x1200 via DP (and ACTIVE Dell Bizlink DP->DualLink-DVI adapter)

    Note that the DP connection only worked with this active DP->DualLink-DVI adapter, the two passive adapters
    I have (which work with my other machines) did not even work in a single monitor setup (even though
    1920x1200 does not require DualLink).

    If I understood the other postings correctly it is crucial that two of the monitors run at the same resolution.

    Best,
    -Duderino

  3. #13
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    Feb 2013
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    Default

    Quote Originally Posted by duderino View Post
    If I understood the other postings correctly it is crucial that two of the monitors run at the same resolution.
    Interesting, I would have thought that your config would require 3 pixel clocks since you have the two 1600x1200 on different outputs (DP & DVI).

    Out of interest, what does xrandr --verbose say your output type and mode clocks are? e.g. something like the following for each output

    Code:
    DVI-0 connected 1050x1680
            ...
            1680x1050 (0x54)  146.2MHz -HSync +VSync *current +preferred
            h: width  1680 start 1784 end 1960 total 2240 skew    0 clock   65.3KHz
            v: height 1050 start 1053 end 1059 total 1089           clock   60.0Hz

  4. #14
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    Apr 2013
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    Default

    Without the --verbose option it says:

    Code:
    Screen 0: minimum 320 x 200, current 5120 x 1200, maximum 8192 x 8192
    VGA1 disconnected (normal left inverted right x axis y axis)
    HDMI1 connected 1600x1200+3520+0 (normal left inverted right x axis y axis) 408mm x 306mm
       1600x1200      60.0*+
       1280x1024      85.0     75.0     60.0  
       1280x960       75.0  
       1152x864       75.0  
       1024x768       85.0     75.1     70.1     60.0  
       832x624        74.6  
       800x600        85.1     72.2     75.0     60.3     56.2  
       640x480        85.0     72.8     75.0     66.7     60.0  
       720x400        70.1  
    DP1 disconnected (normal left inverted right x axis y axis)
    HDMI2 disconnected (normal left inverted right x axis y axis)
    HDMI3 connected 1920x1200+1600+0 (normal left inverted right x axis y axis) 593mm x 370mm
       1920x1200      60.0*+
       1920x1080      50.0     60.0     30.0     25.0     24.0     25.0     30.0  
       1680x1050      59.9  
       1280x1024      60.0  
       1440x900       59.9  
       1280x720       50.0     60.0  
       1440x576       25.0  
       1024x768       60.0  
       1440x480       30.0  
       800x600        60.3  
       720x576        50.0  
       720x480        59.9  
       640x480        60.0     59.9  
    DP2 connected 1600x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
       1600x1200      60.0*+
       1280x1024      70.0     60.0  
       1152x864       75.0  
       1024x768       85.0     75.1     60.0  
       832x624        74.6  
       800x600        85.1     75.0     60.3  
       640x480        85.0     75.0     60.0     59.9  
       720x400        70.1  
    DP3 disconnected (normal left inverted right x axis y axis)
    One more thing: I am not using the stock kernel but 3.5.0-27 (linux-generic-lts-quantal).


    Quote Originally Posted by chrisb View Post
    Interesting, I would have thought that your config would require 3 pixel clocks since you have the two 1600x1200 on different outputs (DP & DVI).

    Out of interest, what does xrandr --verbose say your output type and mode clocks are? e.g. something like the following for each output

  5. #15
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    Apr 2013
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    Default

    The supposedly interesting lines when calling xrandr with --verbose:
    Code:
     1600x1200 (0x49)  162.0MHz +HSync +VSync *current +preferred
            h: width  1600 start 1664 end 1856 total 2160 skew    0 clock   75.0KHz
            v: height 1200 start 1201 end 1204 total 1250           clock   60.0Hz
    
     1920x1200 (0x5f)  154.0MHz +HSync -VSync *current +preferred
            h: width  1920 start 1968 end 2000 total 2080 skew    0 clock   74.0KHz
            v: height 1200 start 1203 end 1209 total 1235           clock   60.0Hz
     
     1600x1200 (0x70)  130.9MHz +HSync +VSync *current +preferred
            h: width  1600 start 1620 end 1700 total 1780 skew    0 clock   73.5KHz
            v: height 1200 start 1201 end 1204 total 1225           clock   60.0Hz
    Not sure what that means (three different clocks? -- I know that this should not be possible).

  6. #16
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    Question

    Quote Originally Posted by duderino View Post
    Not sure what that means (three different clocks? -- I know that this should not be possible).
    Note that there is an active DP adapter in question. Could it be that DP adapter uses different settings and xrandr show actual status of display (not the the settings of the link that drives DP adapter) ?

  7. #17
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    Default

    Quote Originally Posted by chrisb View Post
    Interesting, I would have thought that your config would require 3 pixel clocks since you have the two 1600x1200 on different outputs (DP & DVI).
    I think it depends on the so called crtc thingy and as far as I know you can configure them arbitrarily with xrandr:

    xrandr --output HDMI1/HDMI2/etc. --crtc 0/1/2

    or something like that.

  8. #18
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    Default

    Quote Originally Posted by nadrimajstor View Post
    Note that there is an active DP adapter in question. Could it be that DP adapter uses different settings and xrandr show actual status of display (not the the settings of the link that drives DP adapter) ?
    Probably, the active adaptor is converting the protocol but the end device is still visible to query resolution etc. As far as I understand, DisplayPort monitors do have a pixel clock, but that clock is encoded inside the DisplayPort datastream which has a fixed (162/270/540 MHz) clock. So DisplayPort only requires one clock regardless of number of connected DP monitors.

    Quote Originally Posted by duderino
    Not sure what that means (three different clocks? -- I know that this should not be possible).
    What does "xrandr --verbose |grep CRTC" show? It is possible that there is an extra crtc chip on the motherboard (like Sapphire do with their FleX video cards). I can't think of anything else - you have a DisplayPort and two HDMI ports with completely different resolutions and it works.

    Also, I wonder why xrandr is reporting 6 ports (HDMI1 HDMI2 HDMI3 and DP1 DP2 DP3) when the board only has 3 external ports (HDMI DVI DP)?

    Oddly, I haven't actually found anything in the Intel documentation that suggests it is even possible for two DVI/HDMI ports to share a clock when the monitors are identical, but reports from xorg bug tracker and mailing list say it is. The Intel documentation insists that either one port must be eDP directly from the CPU, or two ports must be DP from the PCH. Weird that Intel don't even mention the possibility of an identical monitor setup, perhaps they don't want to confuse the issue by acknowledging that three monitors off HDMI/DVI can work but only with certain monitors.

  9. #19
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    Output of xrandr --verbose|grep CRTC
    Code:
    	CRTCs:      0 1
    	CRTC:       0
    	CRTCs:      0 1 2
    	CRTCs:      0 1 2
    	CRTCs:      0 1 2
    	CRTC:       1
    	CRTCs:      0 1 2
    	CRTC:       2
    	CRTCs:      0 1 2
    	CRTCs:      0 1 2
    Might this indicate that my mobo indeed has an additional chip onboard?
    The first "CRTCs" belongs to the VGA1 output, so maybe this output can only use CRTC chips 0&1 whereas the others can use 0,1 or 2? I have no clue ...

    Anyway before getting this active DP->DVI adapter, I had limited success with driving the 3 displays via VGA+DVI+HDMI. I could get all 3 of them running as cloned displays at 1024x768.
    But when changing the resolution of either of them, one blacked out or the whole machine froze (maybe because VGA can only access two of the three crtc chips?).

    Quote Originally Posted by chrisb View Post
    What does "xrandr --verbose |grep CRTC" show? It is possible that there is an extra crtc chip on the motherboard (like Sapphire do with their FleX video cards). I can't think of anything else - you have a DisplayPort and two HDMI ports with completely different resolutions and it works.

    Also, I wonder why xrandr is reporting 6 ports (HDMI1 HDMI2 HDMI3 and DP1 DP2 DP3) when the board only has 3 external ports (HDMI DVI DP)?

    Oddly, I haven't actually found anything in the Intel documentation that suggests it is even possible for two DVI/HDMI ports to share a clock when the monitors are identical, but reports from xorg bug tracker and mailing list say it is. The Intel documentation insists that either one port must be eDP directly from the CPU, or two ports must be DP from the PCH. Weird that Intel don't even mention the possibility of an identical monitor setup, perhaps they don't want to confuse the issue by acknowledging that three monitors off HDMI/DVI can work but only with certain monitors.

  10. #20
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    Apr 2013
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    Default

    Here is the output of xrandr --verbose|grep CRTC
    Code:
    	CRTCs:      0 1
    	CRTC:       0
    	CRTCs:      0 1 2
    	CRTCs:      0 1 2
    	CRTCs:      0 1 2
    	CRTC:       1
    	CRTCs:      0 1 2
    	CRTC:       2
    	CRTCs:      0 1 2
    	CRTCs:      0 1 2
    Might this indicate that my mobo indeed has an additional chip onboard?
    The first "CRTCs" belongs to the VGA1 output, so maybe this output can only use CRTC chips 0&1 whereas the others can use 0,1 or 2? I have no clue ...

    Anyway before getting this active DP->DVI adapter, I had limited success with driving the 3 displays via VGA+DVI+HDMI. I could get all 3 of them running as cloned displays at 1024x768.
    But when changing the resolution of either of them, one blacked out or the whole machine froze (maybe because VGA can only access two of the three crtc chips?).

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