HDMI or DVI – monitor connectors

In the past, we only had VGA connectors. With the move to digital TFT displays came the DVI connector. Nowadays, with a graphics card and monitor, we have the choice of connecting the two via either DVI, HDMI or DisplayPort – where DVI and HDMI are more wide-spread still.

Previously, I used DVI because it could provide higher resolutions and refresh rates than HDMI. As my new graphics card came with an HDMI cable I learned something new and new caveats today.

DVI is for image data. DisplayPort and HDMI can transmit video image and audio data. Both support DRM playback (from bluray for example). DisplayPort can have up to four channels in parallel, and can also transmit USB data. DisplayPort is royalty-free; an open standard. Both use packet-based protocols for data transmission.

HDMI has different version numbers. HDMI prior to version 1.4b does *not* support 1080p at 120 hz. This is important to know, as monitor product descriptions often do not actually specify which HDMI version they support. A 120 hz monitor with a 1.4a HDMI port will not be able to display 120 hz when connected via HDMI.

When connecting your monitor via HDMI (potentially the same with DisplayPort), the graphic card driver will initially set the connection up as if you were displaying on a (old?) beamer or TV – bad defaults for your PC to PC monitor. I got very confused when the full resolution did not display full-screen. What you actually have to do is:

  1. Disable scaling
    1. AMD: In the AMD Catalyst Control Center:
      1. Go to My Digital Flat Panels -> Scaling
      2. Move the slider to the right, for 0% scaling
  2. Change the Pixel Format
    1. AMD: In the AMD Catalyst Control Center:
      1. Go to My Digital Flat Panels -> Pixel Format
      2. Change the setting to RGB full

Currently, DVI is definitely still the way to go. DisplayPort will surely take over in the not too distant future. DisplayPort 1.3 supports 5k resolutions and 4k at 120 hz.