A data storage device with a cache memory in communication with a control processor programmed with a routine to effect data throughput with a host device. The data storage device includes a head-disc assembly responsive to the control processor retrieving a host data along with a speculative data in a form of a read data. The control processor adjusting a range for acquisition of the speculative data based on data stored in cache memory fragments of the cache memory. The cache memory storing the read data in an unused cache memory fragment, while the control processor updates a history queue and a band count table based on the acquired read data and releases an oldest cache memory fragment with a lowest count value in the band count table from the cache memory in response to a need for cache memory space.