Abstract: Methods and apparatus for using a predetermined portion of main memory as extended disk buffer memory that is used as disk buffer memory for a disk drive. A controller causes data, such as prefetched data, to flow between disk electronics and the extended disk buffer memory. Data is stored in the extended disk buffer memory along with the logical block address associated with that data and with validation information. Valid data recalled from the extended disk buffer memory can be used directly by the processor without going to the disk drive. In some embodiments the extended disk buffer memory can provide all of the disk buffer memory, while in other embodiments the extended disk buffer memory is augmented by disk drive buffer memory.