Posted by: tfabris
A question about DVI plugs and dual monitors. - 19/12/2006 21:31
My GeForce card on my box at home has two plugs: A VGA plug, and a DVI plug.
I noticed that there were some cables lying around the lab here at work that looked kinda like Y-adapters for DVI plugs.
I'm considering purchasing a second monitor for my home setup. (Once I've got money again, that is.) If I did this, must I use the VGA plug for that purpose, or would one of those Y-adapter thingys work some kind of magic that allows my GeForce card to drive both monitors digitally?
Posted by: andym
Re: A question about DVI plugs and dual monitors. - 19/12/2006 21:44
The dual DVI cards at work (both ATI and NVidia) have a Y-Lead, however the main connector which attaches to the card itself looks like a DVI connector to the casual observer. But in fact it's a much higher density connector.
Posted by: wfaulk
Re: A question about DVI plugs and dual monitors. - 19/12/2006 21:44
I'm no expert, but, in case no one else is, either, my understanding is that DVI handshakes between the source and monitor, so you couldn't have two monitors showing the same thing. In addition, while a DVI can be "dual-link", I don't believe that that means it can control two monitors, only double the bandwidth to one monitor. However, since DVI can carry both digital and analog signals, it's possible that the Y cable splits the digital and analog signals to separate cables. Of course, if that's the case, you're no better off than using the VGA cable. I'd be curious to know the exact set of pins on all three connectors on the Y cable.
It just occurred to me that Bruno probably is an expert on this sort of stuff. Ah, well. I've already typed it in.
Posted by: mlord
Re: A question about DVI plugs and dual monitors. - 19/12/2006 22:51
Mmm.. I suppose if the source was "dual-link DVI-D", and the splitter cable simply separated the two DVI-D links (video outputs), then you'd get nice independent control.
My Inspiron 9300 notebook has dual-link DVI-D ouput, as do the high-end Apple computers. Not much else does, though.
Wikipedia has some great entries for DVI-D etc..
Cheers
Posted by: tfabris
Re: A question about DVI plugs and dual monitors. - 20/12/2006 17:06
Yeah, thanks, Matthew, for re-stating what Andy had said. Sorry, Andy... I had initially dismissed it, not realizing that yes, I was one of the casual observers mistaking the dual-link DVI plug for a standard DVI plug. Yup, that's exactly what those Y-adapters were: Dual-link on one end, and DVI-D on the other. I feel so stupid.
It's really funny. I was reading this thread this morning, and had just had a conversation with a coworker who was setting up a machine, and he said he couldn't get the machine to work with the VGA-only KVM switch because his DVI-to-VGA adapter wouldn't fit the machine's DVI plug. "It looks like a DVI plug, but somehow it's not", he says.
Then a few minutes later I catch up on this thread and it all clicks. We go into the lab, and sure enough, the Y-cables fit the dual-link DVI plug on the machine, and then the DVI to VGA adapter fits the other end of the Y cable.
Sometimes I have to be hit over the head with things before I really understand them.
Posted by: wfaulk
Re: A question about DVI plugs and dual monitors. - 20/12/2006 17:13
What you have is not dual-link. Dual-link is part of the DVI spec that allows a higher resolution on a single monitor. What you have is a proprietary connector that splits out into two different DVI connections, which themselves might be (but probably aren't dual-link DVI).
I'm sure that the end of your cable that plugs into the computer looks like a DVI plug but filled with the small pins and without the four larger pins and blade on one side. I've seen those before, too.
Posted by: tfabris
Re: A question about DVI plugs and dual monitors. - 20/12/2006 17:15
Ah. So the name "dual-link-dvi" refers to a specific technology that's different than what I was just playing with?
Your description of the plug is correct. Resembles a DVI connector on the outside, but inside is filled with smaller, higher density pins, and without the four large blades on one end.
Posted by: drakino
Re: A question about DVI plugs and dual monitors. - 20/12/2006 17:21
Is it an ATI x800 or x850? It's likely a crossfire port then, used for linking two of the cards togther, similar to the NVidia SLI solution.
http://shop.ati.com/product.asp?sku=2768830 is the cable for the x800/850.
Posted by: tfabris
Re: A question about DVI plugs and dual monitors. - 20/12/2006 18:17
The connector pins look the same, but the cable looks different.
The machine had a single video card. In this environment, I find it more likely that it's single card designed to drive a dual-monitor setup, rather than a gaming system with two video cards and SLI.
Posted by: altman
Re: A question about DVI plugs and dual monitors. - 21/12/2006 01:58
ISTR single link has one pair of clock pins and 3 pairs of data pins; dual link adds another 3 pairs of data pins - same clock, double the bandwidth.
Don't think you can split the clock pins between two outputs, but I could be wrong. The video card would have to know how to deal with this though....
Hugo