I was having a rather odd problem with my display recently. My motherboard has onboard video, but I was using a separate nVidia card as my primary display. The video card has an HDMI port and a DisplayPort. I had monitor hooked up via a DisplayPort to mini DisplayPort cable with the DisplayPort hooked up to the video card and the mini DisplayPort hooked up to my monitor.

I was booting into an Ubuntu install, and the problem was that I was getting no display signal at all before X came up. This is a problem, because the hard drive needs a decryption password and I couldn't see when it was asking for the password. I thought it might be an issue of the system getting confused over what the primary video was, as it worked when I plugged into the onboard DisplayPort, and also worked when I plugged into the HDMI port on the nVidia card.

This was a workaround but was annoying as it meant having to swap cables around every time rebooted. Finally I tried replacing the DisplayPort to mini DisplayPort cable I was using to one that had full sized ports on both ends and hooking up into a full-sized DisplayPort on my monitor. This for whatever reason fixed everything, and now the graphics on boot work fine.

I am stumped as to why though. Was using the same exact output port on my PC, tried using two different DisplayPort to mini DisplayPort cables, and two different monitors, got the same effect. Can anyone explain this?

  • Could you please use the EDIT button and break this question up in to meaningful paragraphs? That would make is substantially easier to read. – music2myear Mar 13 at 21:25
  • @music2myear, done. – Joel Croteau Mar 13 at 21:37
  • Excluding issues limited to your own setup, the specification information for mini-DP and DP can be found online. These are public specs and are well documented and generally available. Have you done this research? – music2myear Mar 13 at 22:57
  • In my research there does not appear to be any stated difference between Mini-DP and DP in spec. The capabilities of the two are the same. There are different VERSIONS of DP, but this does not encompass the difference between mini- and macro-. Based on your description of the problem it would seem to me there is a problem with your cable or your monitor's mini-DP connector. Have you tried a different DP-to-mini-DP cable or adapter? – music2myear Mar 13 at 23:02
  • Thanks @music2myear. I'm very sorry I didn't read through the 40-odd page specs for both DisplayPort and Mini DisplayPort and do a detailed compare and contrast from an electrical engineering perspective before asking a question about them online. I'll do better next time. – Joel Croteau Mar 14 at 2:08

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