Second monitor not detected

Question

Hi I have two VGA monitors, my GPU is ATI PowerColor 6850 which has two DVI slots, I use adapters for both VGA monitors. If I connect any the two monitors in the first slot it will work right away (along the plugin confirmation sound). And if I connect any of both monitors to the second slot I won't get anything, nor a signal or confirmation sound.

I also tried auto detecting via Catalyst Control Center and Windows Desktop Resolution. I have the latest drivers installed.

EDIT: I found this on the Spec Description:

Display Connectors DL-DVI-I/SL-DVI-D

And in NewEgg:

2 x DVI (1 Single Link, 1 Dual Link)

Could this have anything to do with my issue?

Solution

Display Connectors DL-DVI-I/SL-DVI-D

THATS your problem

There's three types of DVI connections (well 5, in theory but bear with me).

DVI-D is purely Digital, DVI-A is standard bog standard VGA with a different pin out, and DVI-I is a mix of both. For DVI-I and D you also have single link and dual link, which is irrelevant to the question - it determines maximum resolution.

DVI-I includes analog pins. DVI-D dosen't. As such a passive DVI->VGA adaptor (which is what i mostly see, and is a DVI-A -> VGA converter which you mostly connect to a DVI-I connector) won't work on DVI-D since you're connecting to pins that aren't there

Annoyingly, DVI-D is supposed to have a different pin out just so that you couldn't put a passive adaptor in and find that it dosen't work. The wikipedia article also goes in depth into all this.

In theory you should just use DVI if possible for the second monitor or find an active converter that converts DVI-D to VGA, rather than passes through DVI-A connections to a VGA connector.

Comments

[Myrddin Emrys]

Thought I am not convinced this is the issue, did you try temporarily unplugging something nonessential (such as a DVD drive) and powering up the second set of pins?

[Gabriel]

Thanks I will do that right now, will update once I reboot.

[Gabriel]

Nothing changed :(

[MaQleod]

do you get anything from a voltmeter on the second DVI interface?

[Gabriel]

I don't have a voltmeter

[Gabriel]

Do you guys know what is DVI Single Link and DVI Dual Link, might it be related to my problem?

[Gabriel]

My dell monitor 1908 has one DVI input slot (see this image goo.gl/RRsEi), I don't have the cable to test it right away. But according to what you explained this cable could be plugged into the second DVI port of my GPU, while the old VGA to DVI could still work in the first slot as it does today. Please confirm on this!

[Thalys]

yup, thats how it should work. The DVI-D output on the card will work with a DVI cable connected to a DVI input on the monitor. Leave the VGA connection on the output where it works. Amusingly that has a to spec DVI-D connector.

[Thalys]

Yes. DVI-D cables will go into a DVI-I socket.

[Gabriel]

I love you man! Bought the cable and it worked right away, I didn't even have to scan/identify it.