METHOD AND APPARATUS FOR DATA TRANSFER

PURPOSE:To improve the performance of a computer system, by starting a read- in from a storage device to a buffer when a controller is busy and trying to couple with the controller with a control section through continuous generation of a set sector completion signal. CONSTITUTION:Magnetic rotating body storage devices 30, 30' and 30'', a data transfer device 10 and a controller 20 are provided. In case of read-in, when a head of the device 30, e.g., reaches an objective sector, if the device 20 is busy, an objective record is read in a buffer 16 in the device 10 and this is transferred to the device 20 when the device 20 is idle. In case of write-out, when a head of the device 30 reaches an objective sector, if the device 20 is busy, data are read in the buffer in the device 10 via the device 20 when the device 20 is idle. Next, when the head of the device 30 reaches the objective sector, it is written out.