DVI cable - is dual link bidirectional better?

[Tin_10]

Guys, I have a question. I recieved the hyundai L90D+ 19" today from newegg. It came with a DVI cable, but doesnt seem to have ALL the pins there. It is missing 4-6 pins in the middle of the connector. So I asked someone about this, they said I dont have a bidirectional cable, that its only single link or something of the sort. I am wondering if a bidirectional cable will IMPROVE anything between my x800 pro and the LCD. If you can tell me what the advantages are in having one of these cables, I will buy this one http://www.newegg.com/app/ViewProductDesc.asp?description=12-105-813&depa=0 if its ok, or if u suggest something better from newegg, please feel free to do so.

I guess what I want to know is what the bidirectional cable is, what its purpose is, and if its worth the money. Thanks in advance!

 

[zandor]

Dual link won't do squat on a 19". Here's the basic idea- The TDMS (did I get that right?) standard specifies a certain transmission speed. I think it's a 160MHz dot clock or something like that. Very high res LCDs need a faster connection to refresh at 60 Hz as they have too many pixels for a single link DVI connection. Thus you have 2 choices- analog or dual link. Dual link simply means there are 2 connections sending data to the monitor in parallel so it can refresh at a decent rate. Also, your cable could be missing more than just dual link. Or maybe it has dual link. In the DVI-I plug used on computers there are pins for both analog and digital. Considering that the monitor end is probably DVI-D (even if they use a DVI-I connector just so you can plug either end of the cable into the monitor), there's no need for the analog pins. On a 1280x1024 display, you're well within the limits of a single link connection.
At any rate, don't worry about it. If you're using DVI a new cable won't improve the picture unless your current one really sucks and you're getting all kinds of transmission errors. Since it's a digital connection, that would cause bits to randomly flip. If your cable sucks, you'll see random pixels flashing random colors. If you don't see that, your cable's fine. Save your $$$. Or give it to me. I want a fancy HD-15 -> 5 BNC cable for the Sony GDM-FW900 24" widescreen CRT I just got.

 

[Clank]

I guess what I want to know is what the bidirectional cable is, what its purpose is, and if its worth the money. Thanks in advance!

First things first, there are 3 types of DVI connectors: DVI-A, DVI-D, and DVI-I. Both DVI-D and DVI-I are available in both single link and dual link flavours:

http://www.cablestogo.com/resources/dvi.asp

The difference between the DVI-* connectors is that -A is analog-only, -D is digital only and -I can do either analog or digital. The difference between single link and dual link is the amount of information that can be transmitted at once - dual link can send (wait for it) twice as much as single link, 9.9 Gbps versus 4.95 Gbps. Right now the only monitor requiring the bandwidth of dual link is Apple's 30" Cinema LCD which can do 2560x1600 @ 60Hz. You'll be fine with any good digital single link cable.

As for "bidirectional", that simply means that the cable allows for 2-way transmission of information allowing the monitor (or LCD projector or DVD player or...) to talk back to whatever's connected to it. For monitors it simply allows Windows to query which resolutions the monitor allows. I think all DVI cables are bidirectional regardless of connector or link type, either way it's not really necessary for what you need.

 

[Clank]

Dual link won't do squat on a 19". Here's the basic idea- The TDMS (did I get that right?) standard...

Depends on what you were after. TDMS is Terminal Display Management System, TMDS is Transmission Minimizing Differential Signaling. The first one refers to some archaic database software for OpenVMS VAX, the second one refers to how DVI cables transmit signals. I'll go out on a limb and say you were after the second one.

 

[Tin_10]

ok, so do I have the DVI-a cable? Since I am missing a few pins in the middle. If so, do I need to go get a DVI-D or DVI-I cable, not sure what I currently have.

 

[Clank]

ok, so do I have the DVI-a cable? Since I am missing a few pins in the middle. If so, do I need to go get a DVI-D or DVI-I cable, not sure what I currently have.

Nope, if it came with the monitor it'll be a digital cable. Here's what the various connectors look like:

http://www.datapro.net/techinfo/dvi_info.html#Page05

The analog connector is missing a whole lot more than the middle section. Again, if you look at:

http://www.cablestogo.com/resources/dvi.asp

and read the descriptions on the side, the first cable is a digital single link cable, the next 2 are digital dual link, the fourth is again digital single link.