Input output controller having interface logic coupled to DMA controller and plurality of address lines for carrying control information to DMA agent

摘要

A computer system performs direct memory access (DMA) transfers according to a DMA transfer protocol. The computer system may comprise a Peripheral Component Interconnect (PCI) bus that includes an electrical interface as specified by a PCI Local Bus standard. A DMA agent, system memory, and a DMA controller are coupled to the bus. The DMA controller uses the electrical interface of the PCI bus to control a DMA transfer between system memory and the DMA agent. According to one embodiment, a system I/O controller is coupled between the DMA controller and the PCI bus. The system I/O controller passes DMA control information from the DMA controller to the DMA agent using the electrical interface of the PCI bus. The electrical interface of the PCI bus includes a plurality of address lines and a grant signal line coupled to the DMA agent, wherein the system that I/O controller transmits DMA control information to the DMA agent while asserting the grant signal line.