Abstract: A video controller for automatically varying a memory clock frequency according to the number of commands of controlling a memory includes: a video memory for storing image data to be transmitted to a monitor, a bus interface for receiving commands transmitted from a central processing unit (CPU) through a host bus, a controller for generating an address, data and a control signal for controlling reading from and writing into the video memory according to the commands received from the bus interface, a frequency setter for variably setting a memory clock frequency for accessing a video memory according to an occupancy rate of video access cycles with respect to total bus cycles, and a frequency generator for generating a memory clock according to the memory clock frequency set by the frequency setter.

Abstract: A set top board which is mounted within a personal computer in the form of a card, such as a video card and a communications card, includes: a networking part for communicating with a service provider of the VOD service system; an interface for interfacing with the CPU of the personal computer so that the set top board can be controlled by control signals of the personal computer; a decoder for decoding compressed MPEG image data, and a video processor for processing and outputting data corresponding to the compressed MPEG image data programs as still images on a monitor of the personal computer.

Abstract: A method for using a video memory as a system memory in a computer having a system bios, the system memory, and a video graphic adapter (VGA), includes the steps of examining the system memory using the system bios when the computer switched is on, and determining the size thereof, determining whether to use a portion of a video memory reserved for the VGA as the system memory after referring to an initializing means and connecting the portion of the video memory to the system memory to be defined as an entire system memory when the portion of the video memory is used as the system memory, determining the mode for using the portion of the video memory as the system memory and the mode for using the remaining portion of the video memory as video graphic display, and related register values, initializing the VGA, and jumping to the step of initializing the VGA if the portion of the video memory is not to be used as the system memory.