The Graphic Accelerator Guide

Now Which Parts Of This Video Card/monitor-combo Plays Which Role?

The Monitor plays a crucial role in terms of sharpness, brightness, stability and max. screen resolution of the picture. If you want to have a high quality picture you're asking for a high quality monitor with a big screen, at least 17". Your video card can be as good as it wants, as long as the monitor is crap the screen will still look horrible.

On the video card side, the RAM DAC is the part that is responsible to send the data for a decent picture to the monitor. Two factors are important, the quality of the RAM DAC, e.g. is it stand alone or integrated into the video chipset, and the max. pixel frequency, measured in MHz. A 220 MHz RAM DAC is not neccessarily but most likely better than a 135 MHz one and it certainly offers higher refresh rates - will tell you why further down on this page. RAM DACs tend to be included into the graphic chips more and more now, since it can decrease costs of graphic cards considerably and the quality of modern internal RAM DACs is coming close to the external ones.

The Amount of Video RAM is responsible for the colour resolution in combination with the screen resolution in 2D , in 3D, which is getting more and more important, the amount of local card memory is also determining the maximal 3D resolution . 3D needs much more local memory than 2D for the same resolution. This is due to the fact that 3D needs a front, a back and a Z-buffer. The front buffer holds what you see, the back buffer holds the next picture while it's being processed and the Z-buffer holds the 3rd dimension value (z-value, as x and y make two dimensions, z holds the third). That is the reason why a card with 4 MB local memory can offer a resolution of 1600x1200 at high color (16 bit) in 2D, because it needs 1600x1200x2 Byte = 3.7 MB. However games that are using z-buffer information (and the good ones do, offering you real 3D) can only run at 800x600 x 16 bit color x 16 bit z-buffer, 800x600x6 Byte (2 Byte color front buffer, 2 Byte color back buffer, 2 Byte 16 bit z-buffer) = 2.74 MB. 3D at 1024x768 would require 4.5 MB and can't be displayed by a 4 MB 3D card.

The Type of Video RAM in combination with the Video Chipset is responsible for all performance aspects of the video card/monitor-combo. However we shouldn't forget that the bus system (PCI/VL/ISA/EISA/MCA/NuBus) and therefore also the motherboard and the motherboard chipset are responsible for how fast the data reaches the video card. AGP , the advanced graphic port can offer much higher transfer bandwidth than PCI.