Emulation of Hardware Display Adapter
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18
Techniques are disclosed in which a hardware display adapter such as the IBM Personal Computer (PC) color graphics adapter is emulated by a microprocessor-based display adapter in such a way that existing application software, originally written for the hardware display adapter, can run on the microprocessor-based display adapter without modification. A block of shared memory between a host processor and the microprocessor-based display apparatus is used for mapping the display buffer and its associated control registers. This block of shared memory can be provided with memory protection. A typical hardware display adapter (D/A), such as the IBM PC color graphics adapter (CGA), comprises a display buffer which defines the screen content, and a number of I/O registers to control the screen format, mode, cursor, etc.