Windows "forgets" the Default Monitor

[meepmeep24]

Hi,

We have a small embedded computer with an Intel 945GME chipset and and a single DVI connector on the motherboard. There is an HDMI Monitor connected via a DVI-HDMI Adapter and HDMI Cable (about 25ft). The problem is that sometimes after power up Windows will start to load and the screen will go black. You can hit a Windows softkey (ALT-P or something like that) to scroll through the monitors (of which there is physically only one) and get the display to come up. Here is the problem in more detail:

1. The PC seems to “think” there are 3 monitors (1 real, 2 invisible) installed

2. It will “forget” that the real monitor should be the primary display and default to one of the “invisible” displays

3. We have to manually go into the screen resolution and adjust it so that it duplicates the display on the “invisible” primary display and the “real” secondary display. Power off cycles seem to revert it back to displaying on one display which happens to be the one of the “invisible” monitors. I have uninstalled and disabled the “invisible” displays through device manager with no success. On reboot the computer finds the “invisible” displays again.

This worked in the lab and now it is installed in the field and we cant figure out why this happening. We have systems in the lab and cannot duplicate the problem. Why would windows "forget" the display we set in Windows Display Properties on power up? I think there must be some issue when Windows 7 powers up and queries the monitor - there might be some electrical problem and Windows can not perform some handshaking with the monitor sometimes and Windows switches the default monitor to one of the invisible ones?? We have tried everything in the CMOS and under Display Properties.

Is there a way to permanently set the default display so Windows 7 will not change it? Simply setting the default display under Display Properties is not good enough because it gets changes after a power cycle.

Thanks,
Todd

 

[Aminifu]

Hi meepmeep24,

Try a new HDMI cable (shorter, unless you need the 25ft). You do not need to buy an expensive one, the lower price models work just as well as the expensive ones. When routing the cable do not use any sharp bends (90 degrees or less).

Check the website of your motherboard vendor to see if anyone else has reported this problem with your particular model.

 

[Digerati]

You do not need to buy an expensive one, the lower price models work just as well as the expensive ones.

Normally, I would agree 100% with this (although I normally say avoid the cheapest cables - but you certainly don't need the most expensive).

However, in this case with a 25ft cable, there will be a significant attenuation (signal loss due to resistance) even in the best cables. Attenuation is dependent on the cable's construction quality, conducting materials, and length of the conductors (wires). So IF you really need a 25ft cable, you need a quality cable.

And I definitely concur with Aminifu's suggestion to try another and shorter cable (at least while testing) to maker sure it is the cable, and not the computer or monitor. And if a shorter cable works, and you still need a longer run, try not to buy more length than you need, and get a good cable, but avoid the cheapest and most expensive. That said, I would recommend trying to get the computer and monitors closer together, if possible.

***

One of the problems here (in terms of finding a permanent solution) is you say "sometimes" the problem occurs. Intermittent problems are always the most difficult - especially if you cannot duplicate the problem on demand. If this issue is not associated with the cable length, this could just be Windows getting confused. While Windows 7 is MUCH BETTER with multi-monitor support than previous Windows versions, it still occasionally has issues and so I generally recommend the use of a 3rd party multi-monitor utility. My favorite, and the one I use, is UltraMon – not free, but worth it. Others have suggested the free DisplayFusion, but I have no experience with it.

But frankly, I don't know how they would work with "invisible" monitors - something I have never heard of, and cannot find any information on either. Got a link? I need some learning!