DVI is newer and I suppose better than the old VGA connections for video displays, but why is it better.

It seems like as you go to higher resolutions, with DVI you need to start using dual cables. But not so with the trusty old VGA.

What is so good about DVI that you would accept that disadvantage?

And why HDMI? It seems you get even lower resolution with that? For what? So you can carry an audio signal on the same cable to a video display?

What am I not getting?

The biggie for me is that DVI and HDMI pass HDCP for protected video sources (HD-DVD and Blu-Ray).

DVI and HDMI are digital signals (the monitor converts those signals to a picture). VGA is a analog signal (videocard converts digital signal to pictures). That way your image is way crisypier.

Main point of DVI, HDMI or DisplayPort is digital transfer of signal. You will know what we talk about when you will have to connect a laptop to a LCD display and you will see nice "waves" moving from top to bottom - that is a grounding loop and it happens very often. This doesn't happen with any digital connection.

Wikipedia has good info.

http://en.wikipedia.org/wiki/List_of_display_interfaces

http://en.wikipedia.org/wiki/Digital_Visual_Interface

http://en.wikipedia.org/wiki/High-Defin ... _Interface

with digital connections, output = input. always. with analog connections, output ~=~ input.

bad signals you know well.. the noise on the radio.. the "ant-race" on tv.. and a bad vga output can really look muddy and low in quality.

there are 3 points where a vga connection can kill your image:

digital-to-vga conversion (pictures are digital, the downconversion to analogue, esp. in laptops, can be terrible).
the vga cable. the longer the worse.
vga-to-digital conversion (if you have an lcd screen, or a plasma, or something like that), it will convert it to digital again most likely. and there can be losses again.

with digital, nothing can happen. except actual signal losses, which often result then in no picture at all, or artefacts (those block-things and similar effects)


esp. for higher resolutions, digital is important. analogue can't clearly transport that much pixels sharp and crisp anymore.

But that is when you need two DVI cables, right?

Depends on what you count as high resolution. Up to 2560×1600@60Hz is no problem with a single cable.

VGA is dead. There's very little reason for analog output today when almost everything is digital. Conversion to analog just for the transfer is borderline insane.

The benefit of analog is dramatically increased distance between source and destination. I do Meeting/Show A/V for a living and routinely have XGA (1024x768) runs (industry standard) of over 200' on standard db15 connections. Admittedly this is on mid grade cable from Extron (not the relatively low grade cables that come with your video card or monitor).

I've pushed XGA over 400' with high grade 5 wire BNC and a couple of DA's.

Unfortunately, you can't really range extend digital signals this same way. At least not without significant equipment investments.

I don't understand ... you can actually use two cables? Are you talking about dual-link DVI? Or really dual cables?

Dual-link still uses 1 cable, just with extra pins.

I have no experience with this but it's possible to extend digital signals using CAT5/UTP. I don't think the equipment is that expensive, and CAT5 is dirt cheap. There's probably some restrictions regarding resolution though.

I think there are TFT monitors that uses two cables, but I'm not sure. My point was that high resolution is possible with a single cable.

Yeah, I get you. I guess the way I quoted both of you, it looks like I'm questioning your post specifically. My question was intended to me more general. I've never heard of dual cables.

DVI autonegotiates for resolution and display characteristics.

DVI can support higher resolutions than VGA

TMK, dual link DVI doesnt mean dual cables, but rather using the "unused" pins in the DVI connector. pins that would generally either go to an analog adapter, or pass through sound to an HDMI adapter. instead of these 2 options, they provide extra bandwidth for video to increase the allowable resolution.

this is all before you even discuss the quality differences between VGA and DVI.

I'm running 2560x1600 pixels and 60 Hz on my display. I have one dvi cable. The cable obviously has to support dual link. But if you get a monitor that supports more pixels than 1920x1200, then you will get such a cable bundled anyway. Mine came with two - and that means I could use them to connect two separate sources, NOT that I'd need them both for one source. Actually since my PC is in a closet and my display isn't, I'm running a 5 meter long DVI cable instead, and that cable obviously supports dual link.

So the original poster was misinformed. Two cables are not needed.

The dual link cables are somewhat fat though, as they contain more wires than single link cables. But still at least mine are not any fatter than my VGA cables used to be.

The benefit of DVI and HDMI compared to VGA is, like others have said, simpler signal path that does not contain unnecessary conversion to analog and back and thus resulting in perfect image.

However DVI and HDMI are not free standards and the manufacturer has to pay for every port it puts on devices. Display port standard however is free and hopefully replaces DVI completely. Display port also does not need as fat cable for 2560x1600 as DVI.

Is Display port the connector used by eyefinity?

eyefinity is the multi-display technology used by AMD in their 5xxx series.

you're probably thinking of the 5870 eyefinity 6 edition. and yes, displayport is what it uses.

So the 5450 models, like this POWERCOLOR Go! Green AX5450 512MD2-SD
http://www.newegg.com/Product/Product.a ... ity%205450
use display port connectors to connect to the video displays. And the display port is not proprietary to AMD or anyone else.

Is that correct?

And further if I wanted to display a single desktop accross 3 screens, using that AX5450 512MD2-SD, I could use one
One DisplayPort connection connected to a DisplayPort compatible monitor
One D-SUB connection to a D-SUB compatible monitor, and
One DVI connection to a DVI compatible monitor.

Is that correct?

i would guess that one reason you want the digital interface is because it has higher bandwidth capability.

ces: That's correct.

That says something different. It says that you have to use adapters for the other two video ports to convert them to display port as well. So according to them, you need three display port monitors for this to work properly.

I think they're talking about several possible scenarios, and you're only interested in the first one AFAIK.
This is how I interpret it:

I have to admit that the text is confusing to say the least.

So you interpret that as meaning, if I have a two monitor setup, one on vga and the other running off of DVI - then all I have to do to add a third screen is to be get a third display, make sure it has a displayport input, then use unused display port to drive that third display.

Correct?

Yes. I just saw this, sorry if I was confused.

However, I suggest you keep on searching for more info, since no one here in this thread seems to have any first hand experience with it.

Edited two times, D'oh.

More info here.

Keep searching. . hope you can find some end user opinions.

The way I've heard it explained is that you can use EITHER the DVI OR the HDMI for a single digital output. You cannot use both the DVI and HDMI at the same time.

Otherwise all other outputs on the card can also be used to attach additional montors.

What I want to know is if I XFire two cards can I use the outputs on the second card to attach even more montors?

That is true for most IGPs but not for graphics cards in general.

no, it's definitely true for the 5000 series when it has a DVI and HDMI connection avail. (like my 5770...1x displayport, 1x hdmi, 2x dvi. the hdmi is wired internally to one of the DVI Ports. so using it negates that dvi port.)

That's still two digital outputs.

Yes, but EyeFinity only works from the monitors connected to one single card. In other words if you have say 3 monitors connected to card A, you can add card B to achieve increased performance from XFire. You can't however connect two monitors to card A and then 1 to card B and run them all in EyeFinity - only the two monitors connected to card A will be able to utilize it.

If you just want to use regular multi-monitor output in Windows however, it works - you just can't use XFire at the same time. Any time you want to utilize XFire for increased performance you have to disable the outputs of one of the cards.

Back to the original poster's question, VGA runs into serious trouble when outputting high resolutions like 1600x1200 and above, where you get more noise and attenuation. You need better (read:expensive) RAMDACs on the video cards along with cables and receivers in the displays, and even then the results may not look optimal - can easily be rather blurry even.