2 Replies Latest reply on Jun 11, 2012 5:22 PM by wonderer

    Dual DVI/HDMI output from an i5 2500K GPU with Linux


      I have a Core i5 2500K on an Asus P8Z68-V PRO/GEN3 board connected via the DVI-D port to a monitor as the main desktop display.  I would also like to have it permanently connected via the HDMI port to a TV.  It doesn't have a separate video card.

      Unfortunately if I boot (via MBR) into Linux (64 bit OpenSuse 12.1) with the HDMI cable connected then the monitor goes blank when the GRUB menu should be displayed.  It remains blank thereafter, apart from a brief (<1 sec) display while Linux is being loaded.  The LED on the monitor is green when output is being displayed on the TV, indicating it too is receiving a signal.  It does not display an “Out of Range” message, which would have indicated that the display mode was not supported.  All the output is displayed on the TV OK. 

      If I boot into Windows 7 (via UEFI) with the DVI-D and HDMI cables connected then everything is displayed on both the monitor and the TV.  However when configuring the displays using the Windows Control Panel it shows the TV as display number 1 and the monitor as number 2.

      It's possible to get round the Linux problem by disconnecting HDMI before booting, which gives output on DVI, then re-connecting HDMI and re-configuring OpenSuse again to clone output onto the TV, but it's a pain to have to do this every time.

      The manual says "Note that DVI-D/HDMI dual output works in OS environment only and that during POST or BIOS setup only DVI-D output is valid", which would be fine.  However the evidence from both Linux and Windows suggests that when HDMI is connected it takes precedence over DVI (even in Windows) and only HDMI is valid when booting or even running Linux.

      Unfortunately it's not possible to configure the relative priorities of the graphics ports on the Asus board.  Is this a limitation of: the board, the Z68 chipset, or the GPU itself?

      Has anyone
      managed to get Linux (boot and desktop) displayed via DVI-D when HDMI is already connected on this or a similar board?

        • 1. Re: Dual DVI/HDMI output from an i5 2500K GPU with Linux

          Hi there!


          At this point, the support Intel is offering for graphics controller is limited. Intel recommends checking the Linux software community to get proper drives for your onboard graphics controller.




          If you are interested in additional information see below:





          • 2. Re: Dual DVI/HDMI output from an i5 2500K GPU with Linux

            Hi Allan,


            Thanks for the links.  Asus also said that they don't formally support Linux for that board.


            I haven't tried getting support from the Linux community yet because the relative priority of DVI vs HDMI seems to affect not only Linux and Windows operating systems but also the GRUB boot-loader, which presumably has a very basic generic driver built in.  Even GRUB can display via DVI when HDMI is unplugged. 


            It seems that some part of the graphics system is automatically giving priority to HDMI over DVI, rather than vice versa, when the driver can handle only one.  I can't find much info about the graphics architecture so don't know which component is doing this (on-die iGPU, Z68 chipset, mobo) but was hoping there might be a firmware fix or tweak that would reverse the priorities.


            I would welcome any links to sites that explain graphics architectures, especially Intel HD Graphics 3000 / Z68.  I might then be able to work out where the problem lies and perhaps avoid it in future boards.


            It looks like I may have to buy a separate video card just to get dual output, which is a pity as the on-board graphics do everything else that I want.