HP Vectra XU 6/XXX Optimization Manual page 27

The graphics controller stores screens of data for output to the display in video memory. These
screens of data are called frames and so your video memory is also known as a frame buffer.
Pixel Data
The pixel data stored by the graphics controller defines the color to be displayed for each pixel.
The amount of data required for each pixel is determined by the number of displayable colors;
if you are using only 256 displayable colors, each pixel needs eight bits to define its color (eight
bits gives 256 possible combinations), while in true color modes, each pixel can require up to
four bytes (32-bits).