Hardware Reference
In-Depth Information
Using TMDS, each color channel (red/green/blue) transmits 8 bits of data (encoded as a
10-bit character) serially at up to 165MHz. This results in a raw throughput of 1.65Gbps
per channel. There are three color channels per link, resulting in a maximum raw band-
width of 4.95Gbps per link. Because the data is sent using 8b/10b encoding, only 8 bits of
every 10 are actual data, resulting in a maximum true video data throughput of 3.96Gbps.
This enables a single-link DVI connection to easily handle computer video resolutions
as high as WUXGA (1920×1200) as well as 1080p HDTV (1920×1080 with progressive
scan).
If more bandwidth is necessary, the DVI standard supports a second TMDS link in the
samecableandconnector.ThisusesthreeadditionalTMDSsignalpairs(oneforeachcol-
or)andsharesthesameclockandDDCsignalsastheprimarylink.Thisiscalled
dual-link
DVI
,anditincreasesthemaximumrawbandwidthto9.9Gbpsandthetruedatabandwidth
to 7.92Gpbs,which will handle computer resolutions as high as WQUXGA (3840×2400).
Normally only30-inchorlargerflat-panel displays useresolutions highenoughtorequire
dual-link DVI. Even higher resolution displays can be supported with dual DVI ports,
each with a dual-link connection.
TMDS links include support for DDC, a low-speed, bidirectional standard for communic-
ation between PCs and monitors, created by VESA. DDC defines the physical connection
andsignalingmethod,whereasthecommunicationsanddataprotocolisdefinedunderthe
VESA Extended Display Identification Data (EDID) standard. DDC and EDID allow the
graphicscontrollertoidentifythecapabilitiesofthedisplaysothecontrollercanautomat-
ically configure itself to match the display's capabilities.
DVI uses Molex MicroCross connectors with several variations. The DVI standard was
primarily designed to support digital devices; however, for backward compatibility, it can
