Importance

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Abstract

A RAID controller integrated into a single chip. The RAID controller chip includes a general purpose RISC processor, memory interface logic, a host CPU PCI bus, at least one back-end I/O interface channel, at least one direct memory access (DMA) channel, and a RAID parity assist (RPA) circuit. The RAID chip enables higher integration of RAID functions within a printed circuit board and in particular enables RAID function integration directly on a personal computer or workstation motherboard. The back-end I/O interface channel is preferably dual SCSI channels. The RAID chip is operable in either of two modes. In a first mode, the chip provides pass through from the host CPU interface directly to the dual SCSI channels. This first mode of operation, a SCSI pass-through mode, allows use of the chip for non-RAID storage applications and enables low level manipulation of the disk array in RAID applications of the chip. The first mode of operation permits use of the chip without change to host applications and drivers. Rather, the chip is operable in a manner compatible with known available SCSI controller devices. The second mode of operation, a RAID control mode, provides full RAID management features to the attached host CPU. In the preferred embodiment, the RAID chip presents an Intelligent I/O (I2O) interface to the host CPU to enhance portability and performance of the host/RAID interaction.

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First Claim