Hardware Reference
In-Depth Information
The minimum resolution and color depth (number ofcolors) foruse with current software
is 1024×768 (originally introduced as part of the XGA standard) and 32-bit color depth
for 3D adapters.
Note
For more information about early VGA and VESA SVGA, and XGA standards, see “SVGA
available in its entirety on the disc packaged with this topic.
Digital Display Interfaces
The analog VGA interface works well for CRTs, which are inherently analog devices, but
VGA does not work well for LCD, plasma, or other types of flat-panel displays that are
inherently digital. Video data starts out digitally inside the PC and is converted to analog
when the VGA interface is used. When you are running a digital display such as an LCD
over an analog interface such as VGA, the signal must then be converted back to digital
before it can be displayed, resulting in a double conversion that causes screen artifacts,
blurred text, color shifting, and other kinds of problems.
Usingadigitalinterface eliminates thedoubleconversion,allowingthevideoinformation
to remain as digital data from the PC all the way to the screen. Therefore, a trend back to
using digital video interfaces has occurred, especially for inherently digital displays such
as LCD flat panels.
Laptopcomputershaveavoidedthisproblembyusinganinternaldigitalconnectioncalled
FPD-Link(FlatPanelDisplay-Link),whichNationalSemiconductororiginallydeveloped
in 1995. Unfortunately, this standard was not designed for external connections requir-
ing longer cable lengths or extremely high resolutions. What was needed was an industry
standard digital connection for external displays.
To facilitate a digital video connection between PCs and external displays, several digital
video signal standards and specifications have been available:
• Plug and Display (P&D)
• Digital Flat Panel (DFP)
•
DVI
•
HDMI
VESA released the P&D and DFP standards in June 1997 and February 1999, respect-
ively. Both were based on the PanelLink TMDS (Transition Minimized Differential Sig-
