On my desk I run multiple monitors and have done for many years. I find when doing web design or programming it really helps to have the code on one screen, the test system on another and any reference material in the third. It kinda segregates the work and allows me to get an overview without switching applications all the time. However having multiple monitors made the problem I was about to experience even more of a pain.

I'd always had an issue with my old PC whereby randomly it would either stick in the BIOS or power up with one or more of the displays stuck in standby. Upon investigation windows would either report that everything was fine and the display was connected and switched on with a signal (which of course it wasn't) or say there was no display plugged in (which of course there was). This left me with a couple of options, either climb under the desk and disconnect the monitor and plug it back in again in the hope that Windows would detect it properly, or more often than not simply reboot.

Thinking it was probably just a motherboard or graphics card issue (trying to run 3 DVI displays of an elderly AGP card and a cheap PCI card with an old machine which is tricky at the best of times) I ignored the problem; it wasn't really a show stopper anyway since in those days I left my PC on 24x7. However times have changed and leaving your computer on 24x7 is kind of frowned upon and since it was my electricity bill now I decided perhaps I really should look into this.

The easiest and most gratifying solution was to do exactly what I had been wanting to do for ages anyway, buy a new PC. The old one was in fact old after all and it was about time I sorted that out... However one new Dell with all new graphics cards later and I still had an old problem - although this time not quite the same as it used to be. I still had to power it up multiple times to get all the screens to come on simultaneously but I no longer had the problem were the machine would lock up in the BIOS, this had instead been replaced by a new fault. The machine would boot up but one of the displays would randomly be in super low resolution and Windows would say there was no PnP info. Hmmm... interesting...

Tracing the problem...

After swapping to a completely different PC it was obvious that the problem couldn't lie with the computer and a quick change of the DVI cables showed it wasn't those either (although interestingly enough using VGA cables instead of DVI solved the problem). That basically left the displays themselves.

With 4 or 5 attempts to get the thing booted properly each morning it was time to find and fix the problem even if it meant taking the monitors apart component by component. Of course I could have given in and either used VGA instead of DVI or bought a new pair of monitors but why should I! I didn't have the money for new screens and besides once booted these were fantastic looking TFT's which combined with the crispness of DVI meant I wasn't about to get rid of them.

So to summarise the issues:

• A PC randomly getting stuck in the BIOS
• Monitors that randomly dont come out of standby (one or more at a time)
• Monitors that sometimes don't give out any PnP info (or corrupt the PnP info)
• No problems at all when using VGA cables

It definitely seemed to be a hardware failure of some description. Corrupted communications between the monitor and the computer could easily cause problems with the graphics card which would result in BIOS lockup; so that explained the first problem. The rest all seemed to be caused by intermittent connectivity between the monitor and the PC but that was simply not true... The screens worked fine for weeks and weeks at a time if I left the PC powered on so what could it be?

The Solution!

Desperate for an answer I hunted for firmware updates -nothing- so I did the next best thing and fumbled through the monitor settings for a hardware reset of some kind. On my travels I found something... a menu setting described as "Input Priority". Underneath it had options for D-SUB, DVI-A, DVI-D and auto. It was currently set to auto and from experience I knew that meant it attempted to find a source signal by checking each input individually one at a time. Suddenly a light came on, what if upon power up the graphics card couldn't see the screen because it happened to be checking a different input and didn't respond to the graphics cards requests? That woudl result in very similar problems to I have now!

To cut a long story short, after setting the "Input Priority" to DVI-D (DVI-A is basically VGA on a DVI connector so we don't want that) I am very pleased to report I've had no problems since. So now my good old TFT's have pride of place again and my PC powers up at the touch of a button.

I've no idea what or how many monitors this problem is applicable to but since after hours and hours of trawling through Google I found nothing to help me I thought I'd share this with you...

Posted by Daniel: 19:27, Fri 30th Nov 2007