DMA controller translates virtual I/O device address received directly from application program command to physical i/o device address of I/O device on device bus

A computer system utilizing virtual memory addressing in which commands including information indicating an application program which initiated the commands are written directly to input/output devices comprising:

• a central processing unit,
• main memory,
• a input/output bus,
• a device bus,
• an input/output device, and
• a direct memory access (DMA) controller joined between the input/output (I/O ) bus and device bus comprising:
• means for storing commands directly from an application program including addresses and data designating a virtual input/output (I/O) device address,
• means for translating commands from an application program to determine the physical address of an input/output device on the device bus, and
• means for responding to commands from an application program for transferring data between system memory and the input/output device.

An input/output control unit adapted to be joined to a computer input/output bus in a computer system utilizing virtual addressing in which application programs write commands directly to input/output devices comprising:

• a device bus for joining to a series of individual input/output devices at a plurality of physical addresses,
• a translating circuit for translating between physical addresses of said input/output devices on the device bus and virtual input/output device addresses on the input/output bus,
• a direct memory access (DMA) controller responding to commands directly from an application program including virtual input/output device addresses provided by application programs, and
• a memory management unit within said DMA controller for providing translations between physical addresses of said input/output devices on the device bus and virtual input/output device addresses provided at the input/output bus for data transferred by the DMA controller.