Dueling Interface Standards Jeopardize Takeoff of Flat-Panel Monitors

by David Lieberman, Anthony Cataldo, and Yoshiko Hara

EETimes, June 5, 1998 - A war of connectors threatens to make the transition to digital interfaces for flat-panel monitors a minefield for PC designers. The industry's inability to decide on one standard is putting a damper on efforts to craft a plug-and-play flat-panel monitor interface analogous to the one used in today's analog CRTs, just as the market is beginning to heat up.

Compaq Computer Corp., for one, is putting its money behind the 20-pin connector proposed by the new Digital Flat Panel (DFP) initiative, promising products soon. Other computer manufacturers — notably IBM Corp. — are placing their bets on the Video Electronic Standards Association's Plug & Display (P&D) interface, which uses a 30-pin connector with additional sites for analog links.

Further muddying the waters, an ad hoc industry group of Japanese LCD and systems vendors, called Display Interface Standards for Monitors (DISM), has broached a slate of no fewer than six digital interfaces and brought them under the JEIDA umbrella for standardization. The proposals include 14-, 20, 26- and 40-pin configurations.

"It's potential market chaos," said Mike Marentic, manager of the Flat Panel Technical Center of Hitachi America Ltd. (San Jose, Calif.) and former chairman of the VESA FPD Interface committee. "First we [VESA] couldn't get anyone interested in digital interfaces; now we can't get any two alike."

For all the specs floating around out there, most observers believe the battle will come down to two: DFP and VESA's P&D. The VESA proposal was dealt a blow recently when Intel Corp. and Microsoft Corp. backed off from endorsing it in their most recent PC 99 hardware design guidelines document. Previous versions of PC 99 embraced the P&D solution, but sources said disagreement over the standard and its limited usage prompted Intel to drop P&D in the most recent version, issued several weeks ago.

Meanwhile, Compaq is expected to launch the first DFP-equipped PC before the month is out, and at least two graphics houses — ATI Technology and Matrox — are about to field boards equipped with DFP. Also, Princeton Graphics Systems will shortly announce the first DFP LCD monitor. On the P&D side, several sources said that IBM is planning to unveil monitors and systems with the VESA-backed digital interface early next year.

The two North American interface initiatives did not begin as opponents. When ATI Technologies (Thornhill, Ontario) and Compaq (Houston) first brought the DFP concept to VESA, they presented it as a short-term transitional interface to let people get used to dealing with digital before phasing in the full-featured P&D scheme. But now, several sources said, some are touting DFP as a true alternative to P&D, turning the digital interface issue into what one called "a classic spitting contest" reminiscent of Beta vs. VHS.

Another fly in the ointment is the half-dozen proposals from the Japanese DISM group, chaired by Hitachi and vice-chaired by Toshiba Corp. That slate, according to Hitachi's Marentic, includes types identical to P&D and DFP, along with Sony's Gigabit Video Interface, with its 14-pin connector, and three others.

"In Japanese culture, you have to be inclusive," Marentic said, "so as people proposed things at meetings, the proper thing was to include their proposals. The intent is to have companies produce parts with their own particular implementation, then people can test out what works best."

For their part, the graphics houses and monitor makers — those whose designs are most affected by a changeover to digital interfaces — are generally agnostic in this new religious war. "It would be great if [PC OEMs] would settle on one interface, because [otherwise] this limits the ability to hook any PC to any monitor and ruins the whole future of plug-and-play compatibility," said Mitch Furman, display product manager at Matrox Graphics Inc. (Dorval, Quebec). "Which is why everyone is so desperate to get the connector issues solved."

"We like the idea of DFP for now, but we fully support the P&D standard as a long-term goal, which is why we're pushing for the DFP specification to be as P&D-compatible as possible," said Bob Myers, senior engineer for displays at Hewlett-Packard Co.'s workstation systems division (Fort Collins, Colo.) and chairman of the VESA monitor committee. "If we wanted DFP to be a long-term solution, it would have to be a heck of a lot better than it is, because it has some serious shortcomings."

DFP does share a number of important electrical and logical features with P&D. For starters, the proposal adopts P&D's TMDS (transmission minimized differential signaling) scheme, based on the PanelLink architecture from Silicon Image Inc. (Cupertino, Calif.). It also uses the VESA DDC spec for identification, and the VESA EDID structure for plug and play.

But Hitachi's Marentic cited several points of incompatibility besides connectors. For example, P&D specifies ac coupling while DFP uses dc; and the two use different initialization schemes. Also, DFP excludes the P&D hot-plug capability.

With hot plugging, "If you have, say, a CRT monitor set at SXGA and you unplug it and plug in an XGA LCD monitor, it lets you get the right kind of image up and not be stuck with SXGA CRT-type signals," Marentic said. "But there are no hooks in DFP to allow that to happen. You have to shut the system off and reboot."

Still, HP's Myers believes that if defined right, DFP could send "a great message to LCD monitor makers that they don't have to have multiple designs in their product line. If they want to sell to Compaq, they just stick a DFP connector on the end of it, and if they want to sell to IBM, they put on a P&D connector." That assumes, of course, that the two standards wind up "identical in everything but the physical connector that goes at the host end of the cable," he said.

He acknowledged, however, that things get "sticky" at the retail end. "They [monitor makers] will have to place their bets on which [standard] will be more popular, and there will be conflict in the industry for a while," Myers said.

If the incompatibility issues could be worked out, interchangeability could be "dongled" away, said Marentic — that is, customers could use adapters to connect a DFP PC to a P&D monitor and vice versa. But many shudder at the problems this would mean for PC buyers. "Can you imagine a user going down to Circuit City and trying to sort all this out?" asked Doug Bartow of Analog Devices Inc. (Norwood, Mass.). A spokesman for Number Nine Visual Technology (Lexington, Mass.), said, "Imagine what the return rate's going to be!"

For its part, IBM's stance is that two standards is one too many, even if one is only interim. "DFP is not a standard but a proposal, which has numerous holes in it technically and which is not yet fully defined," said Ian Miller, technical project manager for LCD monitors at IBM's monitor operation in Greenoch, Scotland. "Clearly, any time an industry changes connectors — and the PC industry seems particularly prone to this — it struggles to manage that transition with customers and we end up either with dongles or converters or alternate cables. And it's always messy, expensive and generates unhappy customers. It's worth moving to a digital interface, but we only want to do it once. From my viewpoint, a scenario where you have an interim step and then, 18 months or two years later, try to change again is simply a disaster."

Miller also has performance concerns about DFP. "There's probably little doubt the DFP interface can handle XGA," he said. "At SXGA, you start to raise question marks; and at UXGA, which is not so far away in terms of products, there are very serious question marks." With P&D, on the other hand, "From the outset, we designed it to support UXGA at the very least, with an outlook to extending out to 2.5-k x 2-k types of display when they become available."

Skeptics, meanwhile, are busy speculating about the real deal behind the dueling specs. "There's got to be a reason why all this is happening, and nobody wants to say what it is, but it's not a technology reason," said David Mentley, vice president for display industry research at Stanford Resources (San Jose).

Some point to the fragmentation of the monitor market among an abundance of companies, and call the DFP rush to market an attempt to grab share. Others point to the large share of market that belongs to private-labeled monitors that come bundled with PC systems, perceiving the split as a purposeful attempt to increase that share by locking customers into a particular interface.

According to Scott Macomber, president of Silicon Image, three-quarters of monitors today are bundled with a PC. Indeed, the IBM Consumer Division (Raleigh, N.C.) gets "50 to 60 percent attach rates" of customers buying their monitor bundled with an Aptiva PC, said Jim Bartlett, vice president of marketing there, "and we hope to improve that to a higher percentage."

"I really think DFP will be a short-term solution, a steppingstone to get to where we all know we need to get to," said Bartlett, "and all we'll end up doing is orphaning a bunch of people's products, which will hurt the people who buy them."

Compaq did not respond to requests to state its position.

Work is going on behind the scenes to bridge the differences between P&D and DFP and, as one source said, "to get through this confusion period as quickly as possible." The impending DFP introductions have motivated VESA to start considering a number of practical design issues, such as how to route its USB and 1394 signals, as well as issues such as image scaling and frame rate control that neither P&D nor DFP adequately addresses.

Some observers pointed out that the digital interface matters to only a small portion of the overall monitor market. "Analog plugs in and works, and we believe a lot of customers will require analog, including the vast majority of MIS managers," said Darwin Chang, vice president at Princeton Graphic Systems (Santa Ana, Calif.). "You do lose image stability and get artifacts with analog, but what you gain in broad compatibility and market size is appealing. And you don't have to deal with this [competing digital interface] situation."

Indeed, fragmentation in digital interfaces will be an important factor in people's decision to stay with analog, said Analog Devices' Bartow.

"PC Expo [June 16-18, New York] is a pivotal point for us and a lot of people," said James Chang, product manager for flat-panel displays at Viewsonic Corp. (Walnut, Calif.). "Implementing a digital interface is easy, but what's not is waiting for people to agree on a standard so we can start producing."