In the past, PCI RAID host adapter boards have required several ICs: a processor, a RAID 5 XOR, two to three SCSI ICs, and two independent memory devices- one for RAID firmware and one for disk cache. The Symbios SYM53C1510, a single-chip PCI SCSI RAID I/O processor, delivers a full hardware RAID solution in one 388-pin plastic BGA package. This level of integration enables OEMs to reduce their costs by building a very efficient RAID adapter board or integrating RAID functionality directly onto motherboards. In addition, overall system reliability is increased.The device incorporates a host of advanced features. They include: a customized ARM7 RISC processor with on-chip instruction cache; RAID parity generation and checking hardware; a 32-bit, 33-MHz PCI interface; support for intelligent RAID messaging; a high-speed memory controller that supplies up to 160 MB/s of I/O bandwidth; and two Ultra2 LVD SCSI cores. While supporting a maximum of 30 disk drives, the SYM53C1510 IC is optimized for RAID configurations consisting of from five to 15 drives.The chip's messaging unit efficiently passes messages between itself and other I/O agents. It has a set of four hardware FIFOs for message queuing. Messaging is I2O-compatible. Storage for messages is provided in external local memory. The 32-bit memory controller provides access to flash ROM, SRAM and DRAM. It supports 32-bit EDO DRAM with parity in a 4-Mbyte base configuration. The controller's general purpose 8-bit expansion memory bus supports up to 4 Mbytes of flash ROM.