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Enabling DVI/DP/HDMI and increasing VRAM with Intel Haswell/4th gen HD4200/4400/4600/etc. iGPU

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Can't see what could be wrong with the E7440, sorry.


I've been playing a little more on the multiple external displays arrangement and modified the Azul FB patch for dual DVI outputs:



I can then hook 2 x DVI screens off an E-Port Plus/PRO2X docking station (the wide model with 2 x DVI + 2 x DP ports):



However, initially, I reproduced the DVI black screen issue I experienced at home when attaching DVI + HDMI displays to my E6440:





The screen that went black was the 19" Dell 1908WFP attached to DVI output #1. @1440x900, it's got a lower max. resolution than the 21,5" Full HD Dell P2211H @1920x1080 attached to DVI output #2.


So I thought the issue could be related to resolution. After various adjustments, I found that, in order to obtain video output on both external displays, the larger screen must not be set to a resolution higher than the highest of the smaller screen. Otherwise the screen with lowest capacity goes black or displays snow. But I cannot select just any lower res, some remain incompatible with the smaller screen! 🙄


I could therefore settle for resolutions both screens had in common such as @1360x768/@1280x960/@1024x768 or set the smaller screen to its max. res. @1440x900 and the larger screen @1360x768:

1st_DVI_screen.jpg  2nd_DVI_screen.jpgIMG_1749.jpg


It would also appear that combinations and/or ratios of resolutions applied to the screens may impact video output. For instance, if both screens are set to 1360x768 which is 16:9, I can set the small screen to 1440x900 which is 16:10 and retain full video outputs. I can then set the large screen to 1280x960 which is 4:3 without any impact. If I further reduce the large screen to 1024x768 which is still 4:3, small screen goes black. If I then set the large screen to 1280x1024, I get snow on the small screen. This snow will remain when I return the large screen to resolutions that previously work. If I then set both screens to 1360x768, video output resumes on both screens and I can then set the large one to 1280x1024 without any loss of video! Can make that one out...


NB: If I swap DVI outputs and place the large screen on DVI #1 and the small screen on DVI #2, it's the large screen that goes black.


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Great debug work, Herve! This can definitely be one thing to try.


One question: it's nice that your monitor actually tells you what the problem is! Mine just says "no signal". When the resolution was not correct and the monitor was blank, were you able to find the monitor in SysPref->Display? My problem is that I cannot see this monitor there and I don't know how I can change the resolution (the monitor does show up in IOReg). But you are absolutely correct, my monitors also have different resolutions.


Another thing is that I can never get that display panel work correctly since I installed 10.13.6. It never shows the monitor info even if I use built-in HDMI and video works perfectly. All I get is this:




No monitor or other options can be found.


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Yes, I can see all 3 x displays in the Displays PrefPane at all times; both external displays are properly detected, there's only a resolution issue / conflict / incompatibility. That's shown in my 2nd illustration above.


No display preference tool in OS X/macOS Finder's bar since ML. Look here for alternatives.




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i using Dell Latitude 3440, i see values for VGA in this post , so can i fix VGA after following this post? 

My configuration: i5-4200u,HD4400, VGA mac os 10.12.6 

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