Buh-Bye, DVI

Katherine Stevenson

DVI’s days are numbered, on that we can agree. The digital video interface now featured so prominently on all modern videocards and nearly every modern LCD has reached its performance ceiling. With a maximum bandwidth of 1920x1200, DVI is ill-suited to meet the ever-greater demands of high-def content and it’s incapable of driving ultra-high res screens, like the latest 30-inch LCDs. Granted, Dual Link DVI, which essentially doubles DVI’s bandwidth capacity accommodates a 30-inch screen, but as we’ve learned, even that has issues. (See my 30-inch LCD review in the May issue.)

The fact is, it's time for a new digital interface and three of them are vying for the job. One possible replacement for DVI is HDMI (high-definition multimedia interface), which has been gaining traction over the last couple years as the prevailing video interface in consumer electronics devices—TVs, digital video players, camcorders, game consoles, etc. The relatively small connector is capable of delivering both video and audio signals simultaneously—although the latter is optional; the latest version (1.3) of the spec has a 10.2Gb/s bandwidth capacity, plus support for 10-bit color and lossless uncompressed audio such as Dolby Digital TrueHD. Yet, the interface hasn’t really taken off in PC components—we have yet to see a videocard or LCD that includes an HDMI port.

The backers of HDMI (lead by Silicon Image) hope PC parts manufacturers will adopt the compatible UDI (unified digital interface) standard. Designed specifically for use with a PC, UDI supports 2560x1600 but cuts out some of HDMI’s multimedia features which drive up licensing costs, such as the ability to carry an audio signal or a bi-directional stream. Both HDMI and UDI of course support high-definition content protection (HDCP), although it’s an optional feature. But if PC parts makers are partial to UDI they certainly haven’t indicated as much in their recent products or development roadmaps.

Perhaps the reason why is DisplayPort. We’ve known about this DVI-replacement standard for a couple of years, but wondered whether it would ever come to fruition, especially given HDMI’s growing footprint. Now that the 1.1 version of the DisplayPort spec was just recently ratified, it seems a more realistic option, and it has some key features to recommend it. For one, the spec was created by VESA (Video Electronics Standards Association)—a very influential force in video-interface matters. DisplayPort is also backed by the likes of AMD/ATI, Nvidia, Dell, and Intel—no doubt due in part to DisplayPort’s royalty-free nature, which sets it apart from HDMI, UDI, and even DVI. Like HDMI, DisplayPort is capable of carrying both video and audio over a single, small connector, and it’s capable of 10.8Gb/s bandwidth. Plus, it offers the requisite HDCP support.

The most intriguing aspect of DisplayPort, and the thing that might push it ahead of all others, is its possible use of fiber optics. A company called Luxtera is working with VESA to incorporate its CMOS Photonics technology into DisplayPort, thereby establishing a replacement for today’s copper cable interconnects. While copper cables have been adequate for video demands thus far, the impedance inherent to copper can cause signal loss when tasked with higher-speed, higher-bandwidth data.

At this point, it’s anyone’s guess which standard will eventually make its way into PCs. While it would be super annoying, it could end up being all three—at least they’re all intended to be adaptor-compatible with each other as well as with DVI.


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