I think this is almost relevant for people thinking about buying monitors (I especially like the possibility of longer, lighter cables):
eet.com
IDF: Analog CRT gets a digital update
By David Lieberman
EE Times
(08/30/99, 11:48 a.m. EDT)
PALM SPRINGS, Calif. - Industry consensus around the Digital Visual Interface (DVI) has accelerated the movement away from legacy, analog interconnects and toward a digital path between computers and LCD monitors. Now the venerable cathode ray tube, an inherently analog device, is taking the digital route, with five major vendors set to preview digital-interface CRT monitors here tomorrow at the Intel Developer Forum.
“The DVI specification opens the door for an entire new class of consumer-priced intelligent displays with improved quality and exceptional utility,” said Steve Spina, strategic initiatives manager at Intel Corp. and secretary of the Digital Display Working Group, which defined DVI when the industry was threatened by dueling digital interface standards.
Those other options remain in circulation and have found some acceptance, particularly beyond the desktop. National Semiconductor continues to promote its low-voltage differential signaling (LVDS) digital-interface technology, Sony is pushing its Gigabit Video Interface (GVIF), and the list of digital-interface options from Japan's Jeida standards organization is exhaustive.
But “it's now very clear what the digital interface will be,” asserted John Nelson, director of product marketing at Silicon Image Inc. (Cupertino, Calif.). Consensus on DVI on the desktop, he said, will speed digital-interface design-ins.
It has already sent pundits rushing to revamp their predictions. Nelson noted that the most recent quarterly report from research house Display Search (Austin, Texas) “projected that by first-quarter 2000, more than half of the flat-panel monitors [sold] will be digital-interface.”
Ray Cho, director of business development at Silicon Image, observed that “there will be no analog displays at all” at the developer forum.
“The DVI has definitely become the de facto industry standard for desktop monitors,” said Ken Werner, editor of Information Display magazine (Norwalk Conn.), a publication of the Society for Information Display. “The interface wars have been resolved by a consortium of users [the Digital Display Working Group], rather than a committee of standards moguls.”
But Mitch Abbey, product marketing manager at National Semiconductor, noted that the world of digital interfaces comprises far more than desktop computers. LVDS, he said, has gained success across a broad range of industries, including automotive, telecommunications, medical and test equipment.
Acer, Analog Devices, NEC, Samsung and ViewSonic will come to the forum to show prototype CRT monitors with digital system interfaces based on a new chip from Silicon Image, creator of the PanelLink transmission-minimized differential signaling (TMDS) technology that lies at the heart of DVI. “The last remaining holdout in the desktop digital revolution-the ubiquitous CRT monitor-is going digital,” said Nelson of Silicon Image.
Digital interfaces for CRTs provide “a crystal-clear, sharp image, which is independent of the host computer or connecting cable,” he said. “They make it easier to reduce cost and add functions. And unlike analog displays, the digital CRT is inherently stable.”
Silicon Image's offering is a CRT-specific digital visual controller and receiver chip called the SiI 901. John Hall, director of marketing for Acer Peripherals America Inc., is expected to testify on Tuesday that the chip “enables a consumer-priced digital CRT for the first time.”
Hall will commit Acer to launching “our first DVI-compliant, digital versions of our 17-, 19- and 21-inch flat [face] CRTs in the second quarter of 2000.” He will cite digital's benefits as “improved image quality, a simplified CRT architecture with associated cost savings, and easy integration of new features.”
Marc McConnaughey, vice president of technology and sourcing for ViewSonic Corp., will in turn commit his company to launching its first DVI-compliant digital CRT display in this year's fourth quarter and to delivering digital CRTs “at cost parity with analog CRTs by the end of 2000.” Digital-interface CRTs, he will claim, “deliver a sharper image, have increased reliability and enable elegant display architecture to reduce costs and provide new functionality.”
Down the digital path
For the largely digital flat-panel category, the benefits of replacing a legacy analog link-where a graphics controller in a PC transforms its digital data into analog, only for it to be redigitized at the monitor end-are self-evident. They may be less so for the CRT, with its native analog operation, or the Silicon Image SiI 901, with its analog back end.
However, “there are a couple of issues [in a CRT monitor] you avoid with a digital interface,” Nelson explained. “The quality of the D/A converters in graphics controllers varies, and if a display company can have control over the quality of the DAC, it gives more control over the quality of the image.
“[Also], if you transmit a signal in the analog domain, you need EMI suppression filters, which also vary, even to the point where they limit the ability of a display to receive a pure white signal. And the quality of analog cable varies; its length is somewhat limited, and when you try to add length, it adds costs tremendously.”Image processing is easier in the digital domain than in analog, Nelson added, and it produces better results at lower cost.
“Multisync CRTs have to support the full range of input frequencies, and it's very difficult to design analog circuitry that operates over that continuous range of frequencies. Even just taking the first step of having a digital CRT IC scale to specific step frequencies is a big advantage for CRT companies to improve quality.
“Where we see this heading is the analog portion of a CRT essentially becoming a fixed-frequency electron gun, where all the image processing is done in the digital domain.”
Further, Nelson said, providing “content protection is very easy in the digital domain, [whereas] in the analog domain, it is generally a compromise.”
Moving the parallel D/A converter portion of a CRT video interface into the monitor itself also plays well “in terms of future PC architectures,” with their emphasis on serial interfaces, Nelson said. “It's advantageous to system architecture if you can move the video interface to high-speed serial, just like the rest [of the interfaces]. So over time, the analog interface will be viewed as an add-on option anyway, and eventually it will disappear.”
The Silicon Image CRT chip that is sampling now uses an external triple 8-bit D/A, but that function will be integrated into the chip itself in the next revision, due to enter production in the fourth quarter with unit pricing set at less than $12 in 10,000-piece quantities. The part covers the full DVI performance span, of 25 to 165 Megapixels/second (5 Gbits/s at the top end). It handles formats from VGA (640 x 480 pixels ) to UXGA (1,600 x 1,200 pixels) and can manage an SXGA-format CRT at 85-Hz refresh and a UXGA-format CRT at 60 Hz.
“The obvious next step is to add image processing” to the chip, said Nelson. “We're working with [monitor] partners to identify what areas of image processing are critical to them.”
Silicon Image will announce a companion transmitter chip at the Intel Developer Forum for the host side of a digital interface. The SiI 164 universal digital interface transmitter is available now in production volumes with a very aggressive, sub-$5 price tag in 50,000-unit quantities.
Graphics-board houses Matrox Graphics Inc., Nvidia and Number Nine will demonstrate boards based on the chip at the forum, and Matrox will commit to delivery in October.
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