Generally speaking, DVI cables can be divided into three types of standards. Therefore, you are supposed to have a good command of the relevant knowledge about those cables before you go to buy any equipment in order to upgrade to DVI.
DVI-D - DVI Digital (True Digital)
DVI-D can directly connect the digital signals from your video cards and your monitor. In other words, the signal is completely digital during the whole process without being converted into analog signals. As a result, you are able to get images and videos as clear and vivid as the original ones without any quality loss. On the other hand, the transfer speed is rather fast.
DVI-A - DVI Analog (High-Resolution Analog)
DVI-A is usually utilized to transfer DVI signals to an analog display. Generally speaking, the signal will be carried to the CRT’s and sometimes HDTV’s. In such process, the signal is converted, which leads to the quality to be lost. Nonetheless, pictures transmitted by this format are of higher quality compared with those transmitted by standard VGA formats. As a matter of fact, this format is outmoded and discarded by people in today’s market.
DVI-I - DVI Integrated (Digital and Analog in One Format)
DVI-I is almost standard connection for any video card which is compatible with DVI. It can be used to transfer both analog and digital signals in one cable. However, the cable can only work in a digital-to-digital or an analog-to-analog way, which means that it won’t support the crossovers transmit of either one(digital-to-analog or analog-to-digital).
Last but not least, remember that these three cables cannot be exchanged with other cables. The standards can never be mixed. DVI-D cables cannot be placed on analog systems nor can DVI-A cables on digital systems. However,a DVI-I port can accept another DVI-I, DVI-D or DVI-A cable.