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I have a mini display port output on my laptop and a 27" widescreen LCD monitor that takes in DVI (dual link I presume). To rectify the issue, I purchased a display port to DVI dual link adapter. However, when I plug everything together, the 27" LCD monitor doesn't seem to be able to do any resolution other than 640x480. After two or three weeks of being plugged in, one day, the monitor all of a sudden started displaying the proper resolution of 1920x1200 and I have not changed anything (not even rebooted).

Overjoyed, I used my new monitor for over a month and all was good.

Recently, I went on a rather long trip and took my laptop with me. After coming back, I plug my cables back in and now my silly monitor is back to 640x480 resolution again with no way of changing it. I'm going to leave it plugged in again for a few weeks to see if it suddenly works again.

What is causing this and how do I fix it?

My laptop output - display port
Adapter input/output - display port/dvi dual link
Monitor input cable - dvi-i (yes, I know its not a dual link cable)
OS - Windows 7 ultimate

I know DVI-I can support the standard 1920x1200 resolution, so the cable to the monitor (that it came with) doesn't have to be dual-link capable, and it did work for a month some how, (my guess is voodoo magic), but I would like to know why its doing it.

Since I asked the question, I have left my laptop plugged in and now this morning I notice that the resolution of my monitor is now correct. The only thing I did today was wake it up from sleep.

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Seems like a hardware problem. Have you tried jiggling the cables? – Hello71 Apr 25 '11 at 22:31
up vote 2 down vote accepted

According to wikipedia, your DVI (single link) cable supports 1920x1200 at 60 Hz. Try setting the refresh rate to 60 Hz before changing the resolution.

Try changing the resolution from the graphics card specific settings in control panel (ATI, NVIDIA, Intel) rather than the settings provided with windows.

The fact that it worked for a bit and then stopped working makes me think it could be a bad DVI cable. My resolution starts up at 640x480 when the cable isn't quite plugged in right. If you have a spare DVI cable, try it.

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its not a bad dvi cable since its now working again after leaving it plugged in since I asked the question – z - Apr 26 '11 at 12:51
This does not follow. Bad cables are often only intermittently bad, in my experience. – CarlF Apr 26 '11 at 13:18
@yx The fact that it is intermittent suggests all the more that it is a hardware issue. The dvi cable is not ruled out yet. – James T Apr 26 '11 at 16:52
I'm going to accept this answer not because of the bad cable issue, but I believe it is related to the refresh rate of the display. My machine went to sleep at some point one day and then came back up with the wrong resolution with no way to change it. But changing the refresh rate from 59 to 60 in the control panel snapped it to the right resolution. – z - Apr 29 '11 at 16:22

It could be that the computer is not detecting the display device properly. 640x480 is the default resolution it gives to everything. Right click on the desktop and go to Screen Resolution. From there, click the Detect button on the upper right quadrant of that menu. Does anything happen? What are the names of the display devices here? Can you modify the display resolution of the monitor?

I have sometimes seen this is your secondary monitor is setup to mirror the first. This can cause unexpected results that cause your system to default to a basic resolution. Make sure that you set your computer is sending the proper video signal to both monitors.

Hope this helps.

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it detects the screen correctly when I click on detect, it places a big 2 on the right monitor. I cannot modify the resolution, it is stuck at 640x480. If I mirror both, they both become 640x480. – z - Apr 26 '11 at 12:50
I'm assuming that this laptop uses an Intel Graphics chip. Make sure that you have the latest graphics driver for this laptop. Once installed, you should have access to the Intel graphics manager (I forget the real name). This is a program that has an icon in your system tray that opens up a menu that allows you to modify a large number of settings. – Doltknuckle Apr 26 '11 at 18:38
actually the laptop has an nvidia graphics card in it and I'm running the nvidia control panel to change the settings – z - Apr 29 '11 at 16:21

Maybe it's a problem with your drivers if you have windows update set to automatic, try rolling back the drivers and see if that fixes the problem.

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its not the drivers, I have not updated my drivers for a while either before, or after my trip – z - Apr 25 '11 at 18:08

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