Two video connectors can be found on nearly every PC, monitor or graphics card in use today. Developed 21 years ago by IBM, the analog VGA clings on, despite the rise of the Digital Visual Interface (DVI), which is tailored for LCD displays.
Many newer technologies are being touted to replace VGA and DVI. The two leading candidates are HDMI, which comes on nearly every TV and DVD player today, and DisplayPort, a high-definition alternative created especially for PCs. But Mini-DisplayPort has a powerful backer in Apple Inc., while the emerging wireless HDMI has fans drooling over the potential to dump bulky cables.
The underdog is USB. In the past several years, and almost entirely through the effort of a single Silicon Valley vendor, DisplayLink Inc., USB has become an easy way for laptop users to hook up an external monitor (or two, or three, all the way up to six).
DisplayLink makes graphics chips for laptop docking stations and external USB video cards that connect a laptop to any external monitor up to 1,680-by-1,050 resolution.
DisplayLink shipped just under 1 million chips in its first year, according to Dennis Crespo, DisplayLink's executive vice president of marketing and business development, in an interview last month before the International CES.
Increasingly, monitor makers are embedding DisplayLink into the displays themselves, letting users sidestep buying other gear.
By the end of January, more than 16 monitors will feature built-in USB support, Crespo said.
Besides supporting multiple screens, USB is more compact than bulky VGA or DVI connectors, especially the mini- and micro-USB versions. That makes USB a good candidate for hooking up gadgets like digital cameras or iPhones to monitors or TVs, as well as PCs.
And as its full name, Universal Serial Bus, implies, USB has become ubiquitous since its debut in 1996. The USB Implementers Forum (USB-IF) estimates more than 2 billion USB-enabled devices have been produced.
For all those reasons, "USB is a much more elegant solution" than either HDMI or DisplayPort, said Mark Fihn, editor in chief of the display industry newsletter, Veritas et Visus.
Jon Peddie, head of Jon Peddie Research, is even more enthusiastic on USB video. "USB might kill DisplayPort before DisplayPort kills it," he said.
The chief complaint is the 480Mbit/sec. bandwidth limit imposed today by USB 2.0. While enough to surf the Web or watch DVDs mostly flicker-free, current DisplayLink products run into trouble with 3-D games or Blu-ray DVD playback, Crespo said.
By the end of this year, a new DisplayLink chip combined with improved software drivers should boost frame rates and enable resolutions of up to 2,560 by 1,600, he said.
And when "Superspeed" USB 3.0, with its maximum throughput of 5Gbit/sec. arrives, it should put to rest any fears over USB's support for higher-resolution video and gaming, Crespo said.
But the reality of USB 3.0 lags the hype. A prototype USB 3.0 hard drive shown at CES achieved maximum speeds of 1.3Gbit/sec. reported TG Daily.
TG Daily quoted an unnamed representative from the USB-IF who said that it will be several years before USB 3.0 products start to approach the spec's top speed.
Also, it's unclear whether mainstream graphics chip makers will adopt USB video. Without direct USB output, video signals must travel from the graphics chip through the main system bus before exiting out to the USB port. That could put a cap on USB's video bandwidth, said Fihn, though DisplayLink's Crespo disputed that.
Another key player, Microsoft Corp., is also not supporting USB video in Windows 7, despite supporting the latest, faster versions of HDMI and DisplayPort.
That was because of technical issues, said Chas Boyd, a Microsoft software architect, during a talk at the Windows Hardware Engineering Conference in November.
Crespo said that Windows 7 users will still be able to use USB video, provided they have either a DisplayLink-compatible product or software driver.
Fihn even anticipates resistance from many display makers to adding USB ports because they fear consumers may get confused and "walk up to a monitor and say, 'Oh great, I can plug my mouse in here!'"
Fihn said USB will become a popular albeit niche technology for video, but never become as mainstream as VGA in its heyday or DVI today.