Can't get 3rd monitor to work with Eyefinity - it has DisplayPort!

Mr Davo · 19 Jan 2012

Hi Everyone,

I am attempting to configure EyeFinity with 3 monitors. My graphics card, a PowerColor HD 6850 supports a maximum of 3 monitors, and it sports the following monitor outputs: 2 x DVI, 1 x HDMI & 1 x DisplayPort.

My 3 monitors are all the same brand (Dell) and model (U2212HM UltraSharp), they each sport 1 x DisplayPort, 1 x DVI & 1 x VGA connection.

As all of my monitors support DisplayPort I see no need for a DisplayPort adaptor, and I have connected my monitors as follows:

1). DVI
2). VGA by way of DVI Adaptor (this is because I am using a KVM switch)
3). DisplayPort

Ironically only the 3rd, DisplayPort connected monitor is not working with EyeFinity! I have manually set the connection on the monitor (through the monitor's menu) to DisplayPort. Further when I turn the monitor off and on I see the message: "No DisplayPort " - so the monitor doesn't "believe" that it is connected.

Windows (7 - x64 - Professional) on the other hand responds to the monitor being turned on and off by making the long "doo doo" sound that it typically makes whenever a USB connection is established! However this being said "Screen Resolution" item only ever reports that two monitors are connected!

Furthermore ATI Catalyst can only see two monitors connected - it sees one Analog (due to the adaptor) and one digital (as pictured below).

Any help with getting my 3rd monitor will be greatly appreciated. I have considered uninstally & reinstalling the driver - but I am not convinced that this will help as the monitor is reporting "No DisplayPort Cable"!

Thanks

Davo

**cluberti** · 19 Jan 2012

DisplayPort can technically drive up to 3 monitors, but I am fairly certain that you cannot easily mix it's output with another digital output unless the video chipset can allow it (and this would be high-end, because DVI and HDMI are based on older technology and would require decent amounts of horsepower that a single GPU isn't necessarily going to be designed for). Nvidia makes some laptop video chips that allow splitting the signal between VGA and a DisplayPort port, but that's analog and digital, so it's a lot easier on the chipset than pushing 2 digital outputs at the same time (with content protection, scanning, etc. required by those interfaces).

The latest DisplayPort spec allows daisy-chaining of multiple DisplayPort displays on the same DisplayPort port from a video source, but to do so you need to purchase the requisite cabling or adapters to achieve multimon on the DisplayPort port and all devices along a DisplayPort multimon daisy-chain must be DisplayPort 1.2 spec or higher devices.

There are adapters that you can purchase that can take a DisplayPort signal and output it to multiple DVI endpoints (which could then be downgraded to VGA with an adapter on the DVI port), but you generally need to be driving the same monitors at each endpoint too which can be a pain.