View Full Version : All About DVI

10th February 2003, 08:29
<h2>WHAT IS DVI?</h2>DVI stands for (D)igital (V)ideo (I)nterface.

DVI is a new form of video interface technology made to maximise the quality of flat panel LCD monitors and high-end video graphics cards. It is a replacement for the P&D Plug & Display standard, and a step up from the digital-only DFP format for older flat panels. DVI is becoming increasingly popular with video card manufacturers, and most cards purchased include both a VGA and a DVI output port.

<h2>WHAT ARE THE DVI FORMATS?</h2>There are three types of DVI connections:

1. DVI-D (Digital)
2. DVI-A (Analogue)
3. DVI-I (Integrated Digital/Analogue)<h3>DVI-D - True Digital Video</h3>DVI-D format is used for direct digital connections between source video (namely, video cards) and digital LCD (or rare CRT) monitors. This provides a faster, higher-quality image than with analogue, due to the nature of the digital format. All video cards initially produce a digital video signal, which is converted into analogue at the VGA output. The analogue signal travels to the monitor and is re-converted back into a digital signal. DVI-D eliminates the analogue conversion process and improves the connection between source and display.<h3>DVI-A - High-Res Analogue</h3>DVI-A format is used to carry a DVI signal to an analogue display, such as a CRT monitor or an HDTV. Although some signal quality is lost from the digital to analogue conversion, it still transmits a higher quality picture than standard VGA.<h3>DVI-I - The Best of Both Worlds</h3>DVI-I format is an integrated cable which is capable of transmitting either a digital-to-digital signal or an analogue-to-analogue signal, but it will not work transmitting a digital-to-analogue or analogue-to-digital signal.

Like any other format, DVI digital and analogue formats are non-interchangeable. This means that a DVI-D cable will not work on an analogue system, nor a DVI-A on a digital system. Make sure that you know what format each part of your equipment is before you purchase any DVI cables. Only equipment with a DVI port labelled 'DVI-I' will accept both a DVI-D and DVI-A source signal.<h2>WHAT ARE SINGLE AND DUAL LINKS?</h2>The DVI-D and DVI-I formats are available in either Single or Dual link connectors. These cables send information using a format called TMDS (transition minimised differential signalling). Single link cables use one TMDS 165Mhz transmitter, while dual links use two. The dual link effectively doubles the power of transmission and provides an increase of speed and signal quality; i.e. a single link 60-Hz LCD can display a resolution of 1920 x 1080, while a dual link can display a resolution of 2048 x 1536.<h2>HOW DO I KNOW WHICH CABLE TO USE?</h2>Determining which type of cable to use for your DVI products is critical in getting the right product the first time. Check both of the female DVI plugs to determine what signals they are compatible with.

Note: To prevent pins being broken off of mismatched cables, most manufacturers will make their female plugs with all available pins. This means that most every female DVI plug will look like a DVI-I, but this is not necessarily true. Be sure to look for a label, or check the product documentation to make sure you know what type it is.

If you have plugs that are DVI-D, they will accept a DVI-D or DVI-I cable. If you have plugs that are DVI-A, they will accept a DVI-A or DVI-I cable. If you have plugs that are DVI-I, they will accept any type of DVI cable.

If you have mismatched plugs, such as DVI-D and DVI-I or DVI-A and DVI-I, you may use either a DVI-I cable or the cable that matches the other plug. For example, you may use a DVI-D cable on a DVI-I to DVI-D connection, but not a DVI-A cable.

Note: You may not mismatch a DVI-D and a DVI-A connection.<h2>HOW TO RECOGNISE A DVI CABLE</h2>There are two variables in every DVI connector cable, and each represents one characteristic.

The flat pin on one side denotes whether the cable is digital or analogue:
A flat pin with four surrounding pins is either DVI-I or DVI-A
A flat pin alone denotes DVI-D

The pin sets vary depending on whether or not the cable is single- or dual-link:
A solid 27-pin set (rows of 8) for a dual-link cable
Two separated 9-pin sets (rows of 6) for a single-link cable

NOTE: To distinguish from DVI-I and DVI-A, check the pin set. A solid 27-pin set is for a DVI-l; a separated 8-pin and 4-pin set is for DVI-A.

<table><tr><th colspan="2">Table of DVI connectors</th></tr><tr><td>DVI-D Dual Link</td><td><img src="http://forums.murc.ws/attachment.php?s=&postid=349408" alt="Picture of a DVI-D Dual Link connector" width="154" height="54" /></td></tr><tr><td>DVI-D Single Link</td><td><img src="http://forums.murc.ws/attachment.php?s=&postid=349420" alt="Picture of a DVI-D Single Link connector" width="154" height="54" /></td></tr><tr><td>DVI-I Analogue/Digital</td><td><img src="http://forums.murc.ws/attachment.php?s=&postid=349422" alt="Picture of a DVI-I Analogue/Digital connector" width="154" height="54" /></td></tr><tr><td>DVI-A Analogue</td><td><img src="http://forums.murc.ws/attachment.php?s=&postid=349423" alt="Picture of a DVI-A Analogue connector" width="154" height="54" /></td></tr></table>
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After recent confusion about DVI, digital LCDs and DVI connectors on monitors, I found a rather good explanation of it all. Just thought I'd share it, and note the differences between -D, -A and -I :)


Thread Edited to reduce wasted space. - Sasq

10th February 2003, 09:02
DVI-D Dual Link

10th February 2003, 09:19
DVI-D Single Link

10th February 2003, 09:20
DVI-I Analogue/Digital

10th February 2003, 09:22
DVI-A Analogue

10th February 2003, 09:46
Yeah I posted these links before when you were all getting confoozed during that discussion.


10th February 2003, 09:59
<h3>Pinouts for a DVD-D connector</h3><img src="http://forums.murc.ws/attachment.php?s=&postid=349434" alt="Diagram of the card end face of female DVI-D connector" width="436" height="142" /><table border="1" cellpadding="4"><tr><th>Pin</th><th>Function</th><th>Pin</th><th>Function</th></tr><tr><td>1</td><td>T.M.D.S. Data2-</td><td>13</td><td>T.M.D.S. Data3+</td></tr><tr><td>2</td><td>T.M.D.S. Data2+</td><td>14</td><td>+5V Power</td></tr><tr><td>3</td><td>T.M.D.S. Data2/4 Shield</td><td>15</td><td>Ground<br>(for +5V)</td></tr><tr><td>4</td><td>T.M.D.S. Data4-</td><td>16</td><td>Hot Plug Detect</td></tr><tr><td>5</td><td>T.M.D.S. Data4+</td><td>17</td><td>T.M.D.S. Data0-</td></tr><tr><td>6</td><td>DDC Clock</td><td>18</td><td>T.M.D.S. Data0+</td></tr><tr><td>7</td><td>DDC Data</td><td>19</td><td>T.M.D.S. Data0/5 Shield</td></tr><tr><td>8</td><td>Not Connected</td><td>20</td><td>T.M.D.S. Data5-</td></tr><tr><td>9</td><td>T.M.D.S. Data1-</td><td>21</td><td>T.M.D.S. Data5+</td></tr><tr><td>10</td><td>T.M.D.S. Data1+</td><td>22</td><td>T.M.D.S. Clock Shield</td></tr><tr><td>11</td><td>T.M.D.S Data1/3 Shield</td><td>23</td><td>T.M.D.S. Clock+</td></tr><tr><td>12</td><td>T.M.D.S. Data3-</td><td>24</td><td>T.M.D.S. Clock-</td></tr><tr><td colspan="4"> <h4>Legend</h4><dl><dt>DDC</dt><dd>Display Data Channel</dd><dt>T.M.D.S.</dt><dd>Transition Minimized Differential Signal</dd></dl></td></tr></table>