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Possible Duplicate:
3 Monitors on Sapphire Radeon HD 6870

I have an Asus Radeon 6870 with four places to connect a monitor.

enter image description here

I am using three 1920x1080 monitors, connected to the following ports:

   Card                         Monitor
   DVI    -------------------->    DVI
   HDMI   -------------------->    HDMI
Mini DP   ----> Convertor ---->    DVI

This is the convertor I use: Mini DisplayPort to DVI converter

enter image description here

My card detects all three monitors, but when I go to extend the desktop onto the third monitor, this error comes up and I cannot get all three to work at the same time.

"To extend the desktop, a desktop or display must be disabled." with "Continue" and "Cancel" as options.

I tried the left DVI, the HDMI and I have tried both Mini DPs with the adapter.

I have looked at the other thread on this site in order to solve this problem, still no working solution.

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marked as duplicate by Keltari, Hennes, TFM, Dave M, ChrisF Jan 19 '13 at 22:55

This question was marked as an exact duplicate of an existing question.

I added the extra information gained from this last set of forth and back comments to the post. Can you check if I got it right? After you verified it can you delete the remaining comments to keep the post clean? – Hennes Jan 19 '13 at 19:56
I think the make is "Powercolour", Just checked inside the case to verify. It does look an awful lot like the asus one!… – Dagarian Jan 19 '13 at 20:05

Most modern graphics cards, including this one based on the error, only support 2 display outputs at a time. Even though it detects the third monitor, it will be unable to use it without disabling one of the ports in use.

There are graphics cards that support more than 2 displays out, but they are more specialized cards.

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I have seen other people using the same card in order to get a three monitor display, though! – Dagarian Jan 19 '13 at 16:17
are you positive that the radeon was driving all 3 monitors? Are you sure another video card was not driving the 3rd? – Keltari Jan 19 '13 at 16:21
definitely sure! – Dagarian Jan 19 '13 at 16:22
@keltari Yes, the whole AMD HD 5xxx/6xxx/7xxx series is designed to drive at least up to 3 displays at the same time. And a few even up to 6. The reference cards though come with 4 connectors (2xDVI, 1x HDMI, 1x DP) and to use 3 displays at least one of them needs to use the DP port. – Hennes Jan 19 '13 at 16:24
did some googling, and found an answer... here on superuser, so Im voting to close with a link to the other answer. – Keltari Jan 19 '13 at 16:30

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