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His radeon hd 7770 will only run two monitors

Last response: in Graphics & Displays
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My HD 7770 will only run two monitors. The catalyst center will not even pick up the other monitor. Win 7 will at least detect it but will not allow me to save the settings to extend the desktop. It lists the Acer as Analogue even though I am using the DVI input. I am using two HP LP 2465 and one Acer AL2416WB (DVI-D). I have tried the following configurations:

HD 7770 Video Card DVI to HP LP 2465 (Monitor 1) DVI input
HD 7770 Video Card MiniDisplayport to HP LP 2465 (Monitor 2) DVI input

This configuration works great, but it is only two (2) monitors. It is when I plug in the third monitor that I have trouble. As soon as I plug in the third monitor, one of the two that are already working, suddenly goes black from a loss of signal. I am running Catalyst 12.3.

On the HD 7770 video card outs I have tried the:
DVI+MDP+MDP - only two monitors will work
DVI+MDP+HDMI - only two monitors will work

Could it be a product of the age of the monitors? If anyone has any ideas I am all ears.

Thanks for the help.

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inzone said:
With three monitors you don't want to use the HDMI port and you want to get a DVI cable with two ends so that you can connect two of the monitors with the DVI port and the third with the display port.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...



Why is that? That makes no sense at all. Why bother manufacturing it with the ports if there are permutations that cannot be used, and the idea is to run multi monitors in the first place. I am running into the same problem, however my first mistake was likely purchasing from Best Buy. My suspicion is the need of a larger power supply.
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I believe I am getting to the bottom of this. If using 3 displays, at least one must be mini displayport compatible ... if not, then you must use an ACTIVE minidisplayport adaptor that is also approved by AMD to connect to your third display in whatever way you see fit (HDMI, DVI etc etc).
Passive adaptors will not work, and apparently some active adaptors will not either.

This is very frustrating, and a major black mark against RADEON if you ask me.
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