Cant get full res and DP instability

[RLCCM]

Hi all,
I'm completely stumped, having built a new machine, and spending hours updating and all to get everything working perfectly - which it was for 2 days, until when briefly playing an old game from the secondary hard drive, the screen started flashing on and off, then went dead. The monitor is a dell U2711 and i had been running on DisplayPort in 2560x1440, on windows 7. The grahpics card was ripped out of the old machine - a radeon HD7850.

Ever since then, i've only been able to run a reduced resolution (1920x1080) as the maximum via DP or HDMI, and forced to use HDMI, as the displayport is highly unstable (often doing the same flashing or similar during common tasks, such as viewing photo's, or particularly when playing games again). I've tried swapping the graphics card out to a spare Radeon 4670 I have lying about, but via DVI that still only runs in 1080p.

The only way to get above this 1080p is DVI on the HD7850 - BUT, though windows suddenly allows full 2560x1440, it really doesnt work nicely, text unreadable and a stretched image etc. It turns out on closer examination, in the monitors own menu under "display info" - it shows that its dispaying in "1280x1440" - hence the awful image.

Any ideas anyone? I've completely run out fixes and attempted everything I can, installing and uninstalling drivers and such so often now that its gotten painful, as well as graphics card bios. I just dont understand what it can be, swapping bits in and out as much as i can....

the base spec is that of an i7 4790k on Asus Z97-AR, 2x8Gb Corsair vengeance Pro 2400 and windows 7 64bit.

please help if yu have any ideas

 

[MarkW]

Well, since the monitor is acting up with 2 different video cards, I think its the monitor.

I would try to connect it to another computer to verify this first, but in the end, if its the monitor, you are going to need to RMA it and get a replacement. It you do connect it to another computer, and it works then it may be your motherboard. But I would suspect the monitor first based on what you have said.

 

[RLCCM]

My hope is that it's something fixable, as I wasnt wanting to get another monitor at this stage, I'll try to boot up an alternative machine to try it, and report back - I could try to reconnect my old computer, but it would require the same graphics card from the new machine (or at least one of these already tested) so wouldnt be a completely different rig.

 

[MarkW]

I always have a hard time accepting that two unique devices fail at the same time. Especially when one wasn't even in the computer when the problem started. But it is possible that the problem lies elsewhere, like the motherboard. But the easiest thing to rule in or out right now is the monitor.