The Myth of an HDMI / DisplayPort Standoff

Katherine Stevenson

You hear a lot of speculation about whether HDMI or DisplayPort will be the prevailing spec that computer users should care about. I myself pondered that question a few months back. There’s no doubt in anyone’s mind that DVI and VGA are on the way out. The former, which has remained unchanged since its adoption in 1998, lacks a standards body to help it evolve with the times. And the latter, an analog interface, is incapable of carrying the digital copyright protection that content producers insist upon.

But according to Bruce Montage, a technology strategist for Dell and Chair of the DisplayPort Task Group, despite the two interfaces’ many similarities—greater bandwidth, A/V signal capacity, digital copy protection capability, smaller connector size—DisplayPort and HDMI aren’t actually at odds in the march of progress, but rather serve very distinct purposes.

In a recent conversation I had with Montag, he explained to me that DisplayPort was specifically designed to replace VGA, DVI, and the internal LVDS (low voltage differential signal) interfaces found on computer hardware, while HDMI was created to address the limitations of the S-Video and Component interfaces. And we can see that HDMI has proceeded in that vein, now occupying space on a growing number of consumer electronics products. Still, HDMI is now being found on graphics cards and a growing number of desktop monitors, so what gives?

The lines get blurry with so many people now integrating PCs into their home entertainment systems, or pressing their ever-larger desktop monitors into the service of console gaming and movie viewing.

Still, Montag contends that DisplayPort will prevail on the PC side, and here’s why: The interface standard addresses some issues that affect all areas of IT, and which virtually guarantee its widespread adoption. Right now the LCD on your desk uses an external interface (VGA or DVI) that receives a signal from your GPU, as well as an internal interface (LVDS) that communicates that signal to the display’s panel. By presenting a unified interface, DisplayPort does away with a layer of complexity and enables much physically sleeker (about the width of a laptop lid) and less-expensive monitors. HDMI was designed as an external digital A/V connection to HDTVs.

Another distinction is that DP features a uniquely scalable bi-directional auxiliary channel. Thus, future implementations of the spec can be scaled upwards to support the signals of a monitor’s embedded microphone, USB hub, webcam, etc.—over the same, single cable that carries your video signal. With HDMI, you would need additional cables to be connected to your PC for those devices. Finally, DP is being tuned to take advantage of fiber optic cables, which will allow for even longer cable runs (currently DP using copper is capable of transmitting full bandwidth over an already generous 10 feet of cable) and a cleaner signal.

The fact that a number of large, influential computer parts makers—Intel, AMD, Nvidia, Dell, to name just a few—back the interface add further support to Montag’s argument.

So maybe there is no war, per se, between the two interfaces, and each does provide distinct benefits to the markets they primarily serve, but I’m still not convinced there won’t be casualties. The blurring between computing and entertainment that I spoke of will most definitely affect how parts manufacturers interpret the market’s needs. From the numerous vendors I spoke with this week in preparation for our 2008 Tech Preview, I heard as many different plans for implementing the two next-gen interfaces. So expect to be faced with choices, and be grateful for adapters.

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