Abstract: A disk drive controller includes a memory for storing a plurality of blocks each having a predetermined size, and a parity engine. The parity engine includes a data buffer RAM for storing a block having the predetermined size. A function circuit has a first input terminal coupled to the disk drive controller memory, a second input terminal coupled to the output of the data buffer RAM, and an output terminal coupled to the input of the data buffer RAM. A command circuit, conditions the function circuit and the data buffer RAM to operate in a first operating mode to retrieve a block from the disk drive controller memory and store it in the data buffer RAM, and in a second operating mode to calculate the exclusive-OR (XOR) of a block from the disk drive controller memory with a block from the data buffer RAM and store the result in the data buffer RAM.