Monitor with DVI-I input... DVI-D & VGA??

[champ222]

Morning all...

I currently have two Samsung syncmaster 971p monitors that i use as a dual monitor setup on my pc.

Each monitor has only one DVI-I input that can accept a dvi or vga signal.

The monitor was supplied with a DVI - VGA cable, or you can fit a DVI cable and use that.

i currently use both monitors via DVI into my 8800GTS graphics card.

All works well and has done for years.

Now... the problem... i wish to have another PC that i also want to use Dual monitors on. One solution would be a dual DVI KVM, but that'll no doubt be expensive.

the monitors will accept both digital and analogue signals, and you can manually switch between the two.

so the question is... can i use two cables like this:

To connect one PC to the two monitors via DVI-D and the other PC to the same two monitors via VGA?

Then just switch the monitors from analogue mode to digital mode to select the PC that i want to use?

these cables seem to be designed to be used to connect a DVI-I output from a graphics card to two monitors, one via dvi and one via VGA, rather that two pcs to one monitor, so i would effectively be using the cable the wrong way around.

has anyone done something like this before? any ideas if it is likely to work?

Thanks guys... Sorry for the huge post

 

[aatu]

I'd advice against it

I think those cables are simply designed to offer an alternative coupling method, not to split the signal. As in, if you plug the DVI-I to the PC, and the VGA and DVI-D to two monitors, you probably won't get anything to show on the other monitor. Unless, of course, there's a special feature nVidia has integrated to your 8800GTS, which allows this. But haven't personally encountered such a feature so far...? Have you ever used a passive video cable that has been able to do this? Or are you actually already doing this with your current setup? I know cloning the signal is possible with headphones' audio signal, but never heard this done with a video signal. Without explicit support from the GPU, this is impossible in this situation, because the DVI-D requires digital signal, while the VGA requires analog. So the GPU port would be required to send both signals SIMULTANEOUSLY, which probably isn't possible because there are same pins in use for both signals.

And this sentence kind of puzzled me:
"To connect one PC to the two monitors via DVI-D and the other PC to the same two monitors via VGA?"

I thought the monitors only had one DVI-I connector, nothing else? Not sure where this was going. This is how I see the possible setup:
Monitor1 DVI-I
-> PC1 DVI-D
-> PC2 VGA
Monitor2 DVI-I
-> PC1 VGA
-> PC2 DVI-D

This is assuming both PCs have one DVI-D and one VGA. And the cable used is DVI-I split into VGA and DVI-D, like in your picture.

But in any case, to the actual problem (with how I saw it):
I would think there's no "logical circuitry" in the cable, but only physical coupling, so as long as the PCs aren't ON at the same time, I'd guess it could work. If they're ON at the same time, there could be problems with automatic signal detection, etc. Furthermore, if it really is only physical coupling, the other PC's GPU might get confused when its output port suddenly starts feeding external signal TOWARDS the card...

Though I'd like to say, I have no experience on this sort of dual monitoring, but these are just the things that would first come to mind.

Actually, now that I think about it, the other PC's GPU might REALLY not take kindly to the rogue signal (voltage variation) that's not supposed to get there. There are some delicate circuitries in the GPU. I wouldn't dare to try this unless I was OK with the possibility that the GPU might break from it.

 

[champ222]

Hi. Thanks for the reply.

just to help clarify... i do not use these splitter cables currently. but they exist, so they must be used for something. Some googling suggest that some graphics cards can use these cables to output to two monitors DVI-I out from the graphics card to DVI-D to monitor 1 and VGA (over DVI-A) to monitor 2. Although i have no idea which graphics cards will do this, but some must, else there are several companies making cables that have no purpose at all....

This isnt what i am trying to do however, so i dont really care which graphics cards have this functionality.

this sentence:
"To connect one PC to the two monitors via DVI-D and the other PC to the same two monitors via VGA?"

This is what i mean:

PC1 [VGA1] -----> Monitor 1 [DVI-I] via the VGA section of the splitter cable
PC1 [VGA2] -----> Monitor 2 [DVI-I] via the VGA section of the splitter cable

PC2 [DVI1] -----> Monitor 1 [DVI-I] via the DVI-D section of the splitter cable
PC2 [DVI2] -----> Monitor 2 [DVI-I] via the DVI-D section of the splitter cable

PC2 already has dual DVI ports on it
PC1 could easily be made to have DUAL VGA ports on it

I do see what you mean about the GPU not liking the roque signals tho. and a bit more googling has shown that the analogue part of DVI-I does share a few pins with the digital part. however, if the monitor will work with just analogue RGBHV signals, a quick mod of the VGA cables and all should be fine, at there shouldnt be any shared pins at all that way...

ive got some old hardware kicking about, so i could test it out before connecting it to something important.