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So I have three monitors:

  • One with a HDMI monitor (my "main" one)
  • One with VGA
  • One with the white (and somewhat larger) VGA looking cable

I have the AMD RADEON HD 6450. This has eyefinity, which supports up to four monitors.

If I plug in more than one monitor, it disconnects the other non-main one. In the catalyst control center, if I click "Extend" on the non-working monitor, I get an error:

To extend the desktop, a desktop or display must be disabled.

With the options "Continue" or "Cancel". Both do what you could probably imagine. How do I use three monitors?

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up vote 2 down vote accepted

To use three monitors with AMD Eyefinity at least one of them has to use the display port (either mini or full). This table is in the wikipedia article for 5800 cards but I am pretty sure it applies to the 6450 as well:


If you don't have a monitor with display port as an input you can get an active DisplayPort to DVI-D adapter. I have a 6950 with my main monitor using HDMI one side monitor using DVI-D and the other using this adaptor to DVI. It works very nice the only downside being that occasionally when I wake the computer from sleep the monitor on the adapter doesn't wake up. If I unplug and replug the adapter it works.

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From what I know you need a Display Port connection to use 3 Monitors the same time (so 1 Monitor VGA, the next HDMI and the 3rd must be Display Port).

AMD explains this here:

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