I installed 3 ATI Radeon 5450 graphic cards to support 6 monitors. The first 4 monitors work perfectly. 2 monitors will not show any display and the Device Manager notes them as nPnP. They are definitely PnP. Not sure if I have a bad card or need to change some settings to make the last 2 monitors work
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You can run 6 screens off 2 5450's, that might be it.