DVI cables

DVI cables replace VGA and are being replaced by HDMI and DisplayPort. Here is the inside information on DVI cables.

Single Link

The picture on the left shows a DVI single link cable suitable for images up to 1920 × 1200 pixels at 60 Hz refresh rate, also known as WUXGA. These cables have a bandwidth of 3.96 gigabit per second. A Dell screen failed to work properly at that resolution with a single link cable.

Dual Link

The picture on the right shows a DVI dual link cable suitable for images up to 2560 × 1600 pixels at 60 Hz refresh rate, also known as WQXGA. Dual link cables have a bandwidth of 7.92 gigabit per second. A Dell screen work properly at the the lower single link resolution only when using the dual link cable.

VGA included

There is an option to include an ancient VGA signal in the DVI cable so that cheap displays can fake DVI by using a DVI cable but actually reading the VGA signal. If you have a small old monitor using the VGA link, toss the monitor in the recycling bin.

How do you detect the VGA part. Look at the cable. Look at the wide flat pin on one side. If there are four little pins clustered around the wide flat pin then you have dinosaur VGA. Toss the cable in the recycling bin so the copper can be used for a worthwhile purpose. If your monitor does not work with a proper DVI cable then toss out the monitor.

Alternatives

HDMI

HDMI is fast replacing DVI because HDMI has a built in system to restrict your use of the content you buy. With DVI you can buy a movie on disk then watch it as many times as you like. No matter what rubbish the movie manufacturers put into the disk and the disk reader, you can capture the video output to disk and watch the video repeatedly. HDMI adds an extra locked up section to the video chain and makes it harder to capture the video. HDMI lets the pirates in the movie industry sell you a movie on disk then charge you again every time you try to watch the movie.

DisplayPort

DisplayPort is a potential replacement for DVI and competes against HDMI. DisplayPort has real advantages over HDMI for computer displays and computer manufacturers want to use DisplayPort. Movie manufacturers do not like DisplayPort because the DisplayPort content usage restriction system is optional and movie manufacturers would not be able to force you to pay for a movie you already own.

Cost

2 meter (6 foot) DVI cables can cost over AU$50 but perform no better than $20 cables because the signal is digital. The signal gets through so long as there is an uninterrupted connection. I tested my existing 1.5 metre and 2 metre cables from $25 up to nearly $60 and all produced intermittent results when using a Dell monitor connected to a variety of computers. A 5 metre cable should be worse because the extra length weakens the signal but a new $20 5 metre cable worked better than all the other cables and solved the regular failures of the Dell rubbish.

Note that testing included using several cables supplied with the Dell monitor. Dell supplied their standard DVI cable and it failed. They added in free a special extra expensive Belkin cable, probably because of complaints about the monitor, but still the Dell failed.

The main difference with the $20 cable is the modern manufacturing standards. When all the fancy brands rushed their manufacturing into China, a lot of second rate products filled the expensive branded boxes. Today the standard Chinese cable manufacturers can make a quality tested product for almost the same nothing price as the cheap rubbish. You could probably buy most brands today and find an improvement, except perhaps in a few big American brands where they seem to prefer to spend money on marketing instead of fixing their products.

The low cost dual link cable shown in this page is distributed in Australia by Anyware and they seem to be good at keeping the cost down. The packaging is minimal. The only complaint about the packaging is the plastic bag is not recyclable. Today people are moving from unmarked polyethylene bags to LDPE marked with a recycling symbol. If Anyware talked their suppliers into making that one small change, their DVI cable would be close to perfect.

Quality

If quality is related to cost then quality has nothing to do with the success of a cable for standard use. Gold contacts make a difference if you live in a humid environment because the gold contacts stop corrosion. Do you live near the ocean or sweat a lot? Those gold contacts will resist the fine salt residue you can get on the cable contacts during handling. In most cases another part of your system will fail from moisture or salt before the video cable fails.

You need good electrical shielding if you use your computer in a machine shop or use long cables. Dual link cables appear to be better shielded than single link cables or the extra link wires might absorb stray signals. A cable with a suppressor magnet at each end will help. The following picture shows a magnet around the cable near the plug.

For very long cable runs, perhaps from the front of a lecture hall to the projector at the back in the ceiling, you should use a repeater link designed for the long run, not a DVI cable.

If you constantly disconnect and reconnect cables then look for cables with phillips head plug screws. Constant use could include lecture rooms where every presenter plugs in a different laptop and business/conference centres where big displays are moved from meeting room to meeting room every day. The Anyware cable has a slot in the screw heads for a flat head screwdriver but not the little cross slot for a phillips head screwdriver. Flat head screwdrivers are a waste of time compared to phillips head.

That constant disconnection and reconnection will break the screw heads if they are made of soft plastic. You do not want the screw head to break the first time an inexperienced customer applies too much force to the screw head. A small amount of plastic chipped off the Anyware cable and I expect it would not last a year of daily reconnection but it is so inexpensive you could buy two for less than the cost of some branded alternatives plus some of those expensive brands use plastic that is too soft for frequent use.

Conclusion

Quality DVI cables are not expensive. Dual link is almost the same price and is the better option. New cables are usually better than the rubbish inflicted on us when DVI first arrived. Buy a spare for frequent connection.