Can a GPU (DVI) card output both analogue & digital at the same time?

[dizietsma99]

I've got a high end dual head graphics card.

Head 1 is for my main monitor on my desk.
Head 2 is to be split between my secondary monitor and then down a 5m VGA cable next door to my plasma (which has a VGA-only PC input).

I was going to buy a DVI splitter but have been hearing some rumours that a DVI socket will always autosense whether the monitor that's connected to it is analogue or digital and adjust the output accordingly. (The DVI spitters that I've been looking at still allow cross talk between the first monitor (of the split ones) and the card.)

Apparently the card will never be able to simultaneously output both analogue & digital signals from one head at any one time.

Anyone know if this is true or not?
Many thanks.

Will

 

[Peter]

For the GPUs we currently have in the consumer market, that'll be a solid TRUE. DVI ports are defined to output either analog or digital, depending on what's connected to the far end of the cable.

 

[rbV5]

There are cards that can output both analog and digital from a single DVI-I port using a splitter for certain Matrox cards. Matrox supplies a DVI x dual VGA spitter as well as a DVI x DVI-D + VGA splitter for use on the Parhelia APVe's dual DVI graphics card.

The Matrox DVI x DVI-D + VGA splitter can work for outputting digital and VGA concurrently from at least some ATI AIW cards that are dual head, but only offer a single DVI-I port on the card itself (AIW 9700pro for example).

I'd say its unlikely to work on your card, but it "may" be possible. The splitter themselves aren't really cheap, so if you can't google up someone who's already done it with the card you are going to use it on, be prepared to eat the cost of the splitter.

A secondary graphics card to drive an additional monitor is almost always a better solution than some hack.

 

[Peter]

That's because those Matrox cards actually support more than two heads. Same for those AIW cards - they quirkily implement one DVI-I plug from two separate display engines. This is not at all the normal situation.

 

[rbV5]

Originally posted by: Peter
That's because those Matrox cards actually support more than two heads. Same for those AIW cards - they quirkily implement one DVI-I plug from two separate display engines. This is not at all the normal situation.

Well, obviously

I was going to buy a DVI splitter but have been hearing some rumours that a DVI socket will always autosense whether the monitor that's connected to it is analogue or digital and adjust the output accordingly.

or

DVI ports are defined to output either analog or digital, depending on what's connected to the far end of the cable

cannot be "absolutely" true, otherwise the Matrox solution couldn't work at all, and the ATI hack could also not work.

Same for those AIW cards - they quirkily implement one DVI-I plug from two separate display engines. This is not at all the normal situation.

The OP isn't speaking of a "normal situation" and doesn't list the card in question. I dont know if he has a Parhelia card or not, do you? In any case, it appears pretty clear to me that a DVI port can certainly output both analog and digital signals concurrently....that doesn't mean "his" can.

 

[Peter]

My point is that a DVI-I output that has been implemented to the standard /shouldn't/ be doing this. The purpose of this is to ensure that a digital-capable display unit is seeing /only/ the digital signal, with the analog being a fallback for those that don't.

Imagine a display that has a DVI-I input, so that it can attach to a DVI port or, with an adaptor, to an analog VGA card.
With DVI-I output standard behavior, this display only sees the digital signal, and can't accidentally pick the (inferior) analog copy. On a DVI-I cable from a card that doesn't turn the analog copy off, it'll see both and might choose to use the analog signal although it could very well use the inherently perfect digital one.

 

[dizietsma99]

Thanks for your thoughts guys.

I don't have that card - I have an ATI X1950XTX, and I don't think it will output A & D simultaneously.

So to split it, I think I'll use the DVI-VGA dongle that came with the card, then feed the signal through a VGA splitter (active powered - like a Kramer VP200), then off to each destination. (2nd desktop monitor & plasma).

That should work, no?
Ta.

 

[Peter]

That'll work if you configure a resolution and refresh rate that both displays can handle.

 

[dizietsma99]

Yeah. Unfortunately, they're different resolutions: the Dell 20" widescreen LCD has a optimal res. of 1680 x 1050 and my Pioneer 43" will only accept 1024 x 768, both at 60Hz.

However, I'm resigned to that since when they're both doing their jobs at their respective resolutions, they look fantastic.

I'm prepared to swap resolutions when I switch rooms. (I can setup a profile hot key in the ATI CCC).

My only concern is that the VGA splitter needs to be capable of splitting the 1680 x 1050. (The 1024 x 768 will be fine of course).
The Kramer amp one I've found (the one I put above) says it's capable of UXGA and beyond (which is 1600 x something, right) so it should....

 

[pkrush]

To save yourself the hassle, just get something like a Radeon 7000 PCI or one of the VisionTec PCI-E x1 cards to hook up the third display to.