Easily upgradeable video memory system and method

Abstract

A video memory system is disclosed in which the memory module used to store video data also generates a selection signal that indicates whether the module is a monochrome or color memory module. Memory control logic generates a pixel clock which governs the rate at which pixels of data are output to a monitor, and a load clock which determines the rate at which data is read from the memory module. The load clock is generated at a first rate when the selection signal denotes a monochrome memory module, and at a second, faster rate when the selection signal denotes a color memory module. A shift register receives video data from the video memory module at the rate of the load clock, and outputs that data at the pixel clock rate. The shift register outputs a plurality of bits of the video data in parallel to a video signal generator, which converts the received data into a video signal. To upgrade the video memory system in the preferred embodiment from a monochrome system to a color system, a monochrome memory module is replaced with a color memory module. Alternatively, an upgrade can be effected by adding memory to the memory module and changing the mode selection signal from monochrome to color mode.