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Vga To Dvi Cable - The Ins and Outs of VGA to DVI Cables

digital analog format video

Can I connect the VGA output on my computer to a DVI monitor? This is a common question among casual computer users. The reason the question has become so prevalent is that the industry is in the midst of a transition from VGA to DVI. The good news is that most modern monitors that support DVI support VGA as well. However, one should note that when converting from VGA to DVI, the conversion cannot occur through a passive connection alone. You will need to use an adapter. Read on.

What is VGA (Video Graphics Array)?

VGA is an interface, also known as an RGB or D-Sub 15, which uses a three-row, fifteen-pin connection. There are four styles: HD-15, the DDC2 pin layout, the Mini-VGA, used for laptops, and the DE-9, which the industry rarely uses anymore. HD-15 is a variant of the original DE-9 VGA, and is now the common 15-pin connection we use for HD televisions and for computer video outputs. HD in this case stands for high-density, which distinguishes it from the older, less flexible DE-9, which only had two pin rows.

The VGA format carries an analog component RGBHV signal. RGBHV represents red, green, blue, horizontal sync, and vertical sync. Some VGA cables also have support for DDC2, which is digital clock and data. DDC2 essentially allows the computer to manipulate the monitor configuration electronically. DDC2 is never necessary because it is fully backward and forward compatible.

What is DVI (Digital Visual Interface)?

The Digital Display Working Group (DDWG), an industry consortium, created DVI has a standard that would provide much higher visual quality than VGA could support. This was necessary for televisions based on the newer technologies like LCD and plasma. The goal was to be able to carry an uncompressed video signal while being compatible both with VGA and with HDMI (High-Definition Multimedia Interface). There are three types of DVI formats and a cable for each: DVI-D, A, and I.

DVI-D (DVI Digital, True Digital)

DVI-D provides a direct digital connection between a digital source and a digital display. Since there is no conversion necessary, this format can provide the highest quality image, little data loss, and an extremely fast transfer rate. This is especially beneficial when used between a video card and monitor.

Note: Many manufacturers ship a DVI-I with their monitors for convenience, nonconformity, and savings. Computer users should examine their cable and purchase a DVI-D if they do not have one.

DVI-A (DVI Analog, High-Resolution Analog)

DVI-A carries a digital signal to an analog device. Usually the device would be a CRT monitor, but there are apparently some early model HDTVs that used them as well. There is quality loss due to the conversion from digital to analog, but the result is still better than that which VGA could provide.

DVI-I (DVI Integrated, All-in-One Format)

This is the most common form of DVI, and most TVs, monitors, and video cards that come with a DVI cable, come with a DVI-I. This format does digital to digital and analog to analog, but it does not do conversions between the two formats. This format is convenient, but it’s best to use DVI-D or DVI-A when applicable.

What is a VGA to DVI cable?

VGA to DVI cables have a VGA connector on one end and a DVI connector on the other. Typically, we use these to carry a DVI signal from a video card to a VGA input on a monitor, but we can use them from a VGI source to a DVI input as well. Just as there is DVI-D, A, and I format, there is VGA to DVI-D, A, and I cable. A cable like VGA to DVI-D may seem useless, but it is necessary because DVI formats are not interchangeable, and a VGA to DVI-D cable delivers the analog signal in a format that the DVI-D can accept.

As mentioned in the introduction, you cannot simply connect a passive VGA to DVI cable between a VGA output and a DVI input and expect it to work. The rare exception to this is when the VGA source or the DVI destination has the converter built in. Therefore, it is very important that one purchase a VGA to DVI adapter cable, if necessary, and not simply a VGA to DVI cable. Please note that adapter cables are substantially more expensive due to the additional hardware inside.

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