Compaq Computer Corporation, Inc.

Hewlett-packard Development Company, L.p.

Christopher Garza

Albert H Chang

Ryan A Callison

William C Galloway

Mark J Thompson

Jeff M Carlson

Hubert Brinkman

A single read request to a memory controller generates multiple read actions along with XOR/DATUM manipulation of that read data. Fewer memory transfers are required to accomplish a RAID/DATUM parity update. This allows for higher system performance when memory bandwidth is the limiting system component. In implementation, a read buffer with XOR capability is tightly coupled to a memory controller. New parity does not need to be stored in the controller's memory. Instead, a memory read initiates multiple reads from memory based on an address decode. The data from the reads are multiplied and XOR'd before being returned to the requestor. In the case of a PCI-X requestor, this occurs as a split-completion.

Memory controller interface with XOR operations on memory read to accelerate RAID operations

A memory interface controller employs a DATUM multiplier within a destination address to perform DATUM RAID operations. If destination data is in an XOR memory address space, then the multiplier can indicate to multiply source data by the multiplier and XOR that resulting data with the destination data. The DATUM multiplier can be read in response to detection of a memory command. The multiplier alternatively can be used in connection with an input/output bus write command to write source data from the input/output address space to an XOR memory address space. In response to such a write command, the input/output bus data in the input/output address space is multiplied by the multiplier; that resulting data is XORed with the destination data in the XOR memory address space. The multiplier in this case can be within an input/output bus address associated within the input/output bus data.

Memory interface controller for datum raid operations with a datum multiplier

A memory interface controller includes a read buffer to pipeline data from a synchronous dynamic random access memory (DRAM) in response to a plurality of consecutive SDRAM burst read requests, a write buffer to store write data, an exclusive or (XOR) engine to XOR the write data with the data from the read buffer, and a write interface to write resulting data from XORing the write data and the data from the read buffer to the synchronous DRAM. Data is pipelined in the read buffer by repeatedly issuing an SDRAM burst read request before data is transferred out of the synchronous DRAM in response to a previous SDRAM burst read request until a desired amount of data is stored in the read buffer. The memory interface controller thus can perform an external read-modify-write cycle for the synchronous DRAM. The synchronous DRAM can serve as a RAID (Redundant Array s of Inexpensive Disks) memory.

Raid XOR operations to synchronous DRAM using a read buffer and pipelining of synchronous DRAM burst read data

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Christopher Garza