Radeon 6870 w/ 3 LCDs - problem

Hi folks,

I just upgraded from a 2gig 4890 to a 6870 this morning. Installed and working fine but I'm having a problem connecting all three of my LCD monitors and so have some questions about port connectivity with this card.

Where the card comes with a DL-DVI port, a DVI port, an HDMI and 2 mini-displayports, I have two monitors connected right now:

I picked up a DVI to mini-displayport adapter for monitor 2 and plugged it into the 1st mini displayport. It works fine at the native 1920x1080 and looks good.

I have my main monitor (1) hooked up as DVI to DVI. It runs correctly at its native 1920x1200 and looks good.

The problem is monitor 3, or the one on the left. This is a Samsung 2233sw with DVI and VGA output ports. I currently have it connected via a VGA cable into a VGA mini displayport adapter into the 2nd mini-displayport on the video card. While it's working, it only runs at 1600x1200. It refuses to display at the monitor's native 1920x1080 and it looks pretty bad. I've tried reinstalling the monitor driver, letting W7 pick its own and so forth. No matter what I do it won't let me select the optimum resolution of 1920x1080. I'm wondering why not. My understanding is a VGA cable can support 1920x1080 (and above), but is it possibly not jiving well with the mini-dp adapter? I can connect it using a DVI to DVI cable in the second DVI slot but it seems the radeon 6870 won't let you use both DVI ports at the same time and W7 won't even find the monitor that way. There's an HDMI slot free on the video card but I'd need a DVI to HDMI cable for that and I don't know if that will support 1920x1080.

So, I'm stumped. Any ideas? Headed to a cable store on Monday so hopefully will have the right answer on what the best buy (ha) is to get the right resolution. Thanks in advance to anyone with appropriate info.

4 answers Last reply
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  1. You need to pick up another mini-display port to DVI adapter and connect it to that Samsung of yours..... it'll work fine after that. Mixing digital and analogue adapters will cause excessive strain on your GPU..... it's also more stressing to have them all setup on different resolutions.
    I'd suggest go for the disp-DVI adapter and connect it to the Samsung.......
    If you don't want to do that, then a simpler way is to just exchange the monitor with that native resolution ..... but then again it's 1600 and not 1920....
    better buy another adapter
  2. Thanks Alyoshka. I'll pick up another DVI-mini-displayport adapter today. Any idea why the card won't run two screens via the DVI ports at the same time, if something is plugged in in any of the other ports?
  3. Well, that didn't work. I picked up a DVI-HDMI cable and plugged the third LCD into the HDMI port - no good. It won't save the display settings. I receive the general 'unable to save display settings' error when trying to extend the desktop to LCD 3. As a back-up, I picked up the recommended DVI-to-mini-DP adapter and hooked LCD 3 up from its DVI port into the adapter and then into the second mini displayport on the video card. Same issue. Not sure what the problem is here.

    Since I have one LCD in the first DVI port, and a second in the first mini DP port, I can't seem to get any success in connecting the third LCD to any of the ports and getting it to run at its native 1920x1080. It'll run at 1600x1200 but looks very bad. Solutions? I don't understand why they'd put 5 ports on the back of the video card and not provide clear indications of the limitations on using these ports.
  4. This topic has been closed by Mousemonkey
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