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I am still trying to understand the difference in signals sent by different DVI ports. My graphics card has a DVI-I port (4pins) and my monitor has VGA. I bought an adapter and the adapter is for DVI-D to VGA. I know the card is working because I have plugged it into another monitor with with a DVI-I cable. I want to know if maybe I didn't install the right drivers, or if I goofed and bought the wrong adapter.

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DVI has a number of possible configurations:

  • DVI-I ("I" stands for integrated; combines digital and analog in the same connector; digital may be single or dual link. Analog is the VGA signal.)
  • DVI-D ("D" stands for digital only; again, can be single link or dual link.)
  • DVI-A ("A" stands for analog only; I've never actually seen one of these)

The connectors look like this (courtesy Wikipedia):

enter image description here

The four pins on the right are used for the analog signal.

Since the card has DVI-I output, the analog signal is already there. You can use a passive DVI-I to VGA adapter to grab the output from the correct pins to feed a VGA monitor.

A DVI-D adapter would need to be an active converter that takes the digital signal and converts it to analog to feed the VGA monitor. There are some fake adapters out there that are sold as DVI-D to VGA, but don't actually contain a converter. However, a real one will work, also. It will be more expensive than a simple passive adapter.

  • Just to muddy the waters a bit: it's not uncommon for graphics cards to have a DVI-I connector for compatibility with DVI-I cables, but to not send any signal to the analog pins. – duskwuff May 25 at 22:01

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