In 1987 IBM introduced the VGA standard, which allowed the use of 640 × 480 with 256 colors. Over the years, there were patterns SVGA (800 × 600), XGA (1024 × 768), SXGA (1280 × 1024) and so on, used by the monitors present. Nevertheless, the same analog VGA connector (Mini D-Sub) 15-pin is still used today.

The big problem is that CRT monitors were eventually replaced by monitors LCD, which are digital in nature. To maintain compatibility with older cards, they (monitors) include analog / digital converters, which also increase the cost of equipment, reduce the image quality.

To solve the problem, created the standard DVI (Digital Visual Interface), which allows the signal is transmitted in a digital video card to the monitor, eliminating the need to convert digital> analog> digital, which causes degradation image.

There are several sub-patterns within the DVI. Most cards use DVI-I, which maintains compatibility with old monitors while offering the digital signal and analog. This allows you to connect an analog monitor to a video card with DVI-I using a simple adapter:

Most cards also offer low cost one DVI and one VGA. However, an increasing number of boards are to come with two DVI connectors, or two DVI and one HDMI, making it necessary to use the adapter to connect to VGA monitors. It's always good to have one of them or by hand, since the VGA output are becoming increasingly rare in new video cards, but the monitors will still be used for a long time.

Another situation in which you will need adapters is to use two monitors using TwinView. The main reason for so many cards offer two DVI and no VGA is that you can use adapters to connect the VGA DVI outputs, but there are adapters to connect a DVI to VGA output.

The TwinView is also supported on Linux through the binary drivers from nVidia. Just run (as root) the command "nvidia-xconfig - twinview" so that it detects the monitors and manages the configuration and then set the desired options through the nvidia-settings:

Further, the DVI supports the use of single-link connections and dual-link. Each data link is formed by three independent channels (one for each color), 8-bit and 165 MHz, which results in a transmission rate of 3.96 gigabits for the single-link DVI and 7.92 gigabits for the dual-link DVI . As in the SATA and PCI Express, for every 8 bits of data are sent 2 additional bits of timing (bringing the total gross to 4.95 and 9.9 gigabits), which eliminates the need for a separate clock signal.

A single-link connection supports the use of up to 1600 × 1200 (with 60 Hz refresh) and a dual-link support the use of 2048 × 1536 (at 75 Hz) or 2560 × 1600 (at 60 Hz, which is the refresh rate used by most LCD monitors). As we are talking about a digital link, there is great flexibility. It is possible to achieve higher resolutions by reducing the refresh rate, for example, but that's not very common, which causes loss of fluidity of the image, anyway, there is still much demand for monitors with resolutions above 2048 × 1536.

The single-link cables have two columns of pins less, but are physically compatible with the dual-link connectors:

You can connect a single-link on a card with dual-link connectors without any problems. The reverse (a single-link card with a dual dual-link) also works, but in this case you are limited to 1920 × 1080, regardless of the resolution supported by the monitor. One observation is that many cheap video cards use dual-link connectors, but in fact operate only in single-link. If you want to use a high resolution monitor, always check the specifications of the board.

Although it seems an exaggeration, many LCD monitors 30 "already support the standard WQXGA (2560 × 1600) natively, such as Apple cinema 30IN, the HP LP3065 and Dell 3007WFP. With the falling prices of LCD monitors, these monitors will become increasingly common, given to those who need a large workspace for working with image editing or CAD, or just want a giant monitor to unleash the full power of the GPU.

In addition to the DVI-I, there are also DVI-D, which carry only the digital signal, leaving the possibility of using the adapter to connect an old monitor. The only visible difference between the two is that the DVI-D does not have the pins C1, C2, C3 and C4, which are used by the analog signal:

Cards with DVI-D are still relatively rare, since the DVDI-I combines the best of both worlds, but the DVI-D can turn the tables in the future as the compatibility with older monitors are slowly ceasing to be a concern . Adopt the DVI-D allows manufacturers of video cards and cards to remove the onboard digital / analog converter, which reduces a few dollars in the cost of production.

One example is the Gigabyte GA-MA785GM (based on the AMD 785G chipset), which offers a DVI-D, complemented by an analog VGA output and an HDMI output (which is essential to build an HTPC, since it is the interface more used in HDTVs). It supports the use of two monitors simultaneously, but as the DVI and HDMI share the same tracks of the board, you can not use them both:

You can also connect a video card with DVI output to an HDTV using an HDMI connector. Both DVI and HDMI use the same pattern of signs, so you need only buy a single cable. The limitation here is that the DVI does not include the pins for the sound, so you must use a separate audio cable, connected to the sound card.

A term associated with the HDMI is HDCP (High-Bandwidth Digital Content Protection), a technology less noble, which is intended to "protect" the film industry of thieves content (consumers), providing a way to protect and encrypt movies and series on Blu-ray.

What differentiates the systems prior HDCP encryption, such as the CSS used on DVD, is the fact that it is far more intrusive, requiring the combination of an operating system, a playback software, a video card and a monitor compatible with the standard, otherwise the signal is high-resolution blocked in digital connections.