Abstract: A video controller board for supporting AX Japanese modes and enhanced VGA modes. The board includes two EGA video controllers to support the AX standard and a VGA video controller to support the enhanced VGA standard. Video memory sufficient to support the AX standard is shared by the VGA and EGA controllers. An interface renders the diverse protocols of the VGA and EGA controllers compatible with the shared memory so that each controller sees the memory in a configuration in accordance with its own protocol.

Abstract: A PC video adapter board for driving a VGA color monitor, the board including a VGA video color palette DAC for providing analog color video to the monitor. A VGA controller provides VGA digital color video signals to the DAC through a first multiplexer and timing signals to the monitor through a second multiplexer. The board also includes EGA video controllers and a Japanese EGA (JEGA). A read/write register is written from the computer to contain additional EGA digital color bits for supplementing the six JEGA bits so as to provide a full eight bits of digital video in the EGA modes. The register provides a control bit to switch the first and second multiplexers between the VGA and EGA digital color video and timing signals.