CRTs are an analog technology. The video data inside the PC is manipulated digitally, converted to an analog signal by the graphics adapter, and delivered to the CRT monitor, which can use the analog signal directly. Except for a few high-end models that can use discrete RGB connectors, CRT monitors universally use the standard 15-pin analog VGA connector.
Conversely, FPDs are inherently a digital technology. Although most FPDs can accept both analog and digital signals, using an analog signal requires converting that signal to digital before the FPD can display it. This double conversion—digital-to-analog inside the PC followed by analog-to-digital inside the FPD—reduces image quality and increases complexity and costs, but in a world of analog video adapters, FPD makers had no choice but to design their displays to accept analog inputs.
It would obviously be simpler to avoid the digital-to-analog-to-digital conversion and drive the FPD directly with the digital signal generated by the PC, and that’s just what is done with new-generation display adapters and FPDs. But getting to that point was not simple.
The first efforts to standardize a digital interface for video began in 1996, but made little progress initially. Early efforts centered on adapting the well-established Low Voltage Differential Signaling (LVDS) standard in use for notebook systems to desktop systems. LVDS could not be used as is because it was designed for the short cable lengths used in ...