NVIDIA TwinView Vs. Matrox Dual Head
The digital 2D/3D engine alone is not able to draw a picture onto your monitor as the digital data has to be converted into an analog signal in order to display something on a CRT monitor. That is done by the RAMDAC (digital analog converter), which is nowadays found inside the graphics chip. The higher its clock, the higher the screen resolutions and refresh rates.
Modern RAMDACs work at up to 360 MHz, which is enough for resolutions up to 2048x1536 at 85 Hz. Only a few years ago, the DAC was a stand-alone component on every graphics card. Thanks to structure sizes of 0.18 µm today, the integration into the die is quite easy to realize.
For two monitors a second RAMDAC is required, unless one of the two monitors should be a digital flat panel. Matrox successfully integrated this second DAC into some of their products for years now. Today the second DAC is part of the G400 or G450 chips. Usually the second DAC is not as fast as the primary one. However, today every dual monitor graphics card can display up to 1600x1200 at reasonable refresh rates.
NVIDIA went a different way with their technology called TwinView. Basically, the GeForce2 MX chip includes everything to run two monitors - except the second RAMDAC. This is slightly more expensive for dual solutions than the way Matrox handles this, but in exchange it makes the chip itself cheaper thanks to less required die space. Right now, a well-equipped TwinView card is slightly more expensive than the Matrox G450. In return you will get clearly better 3D performance.
