| 摘要 |
PROBLEM TO BE SOLVED: To effectively utilize plural look-ahead mechanism in a system provided with the look-ahead mechanism for locking data ahead from a memory and preparing for a read request from a master. SOLUTION: At the time of requesting data transfer to an input/output device 20, a device driver selects the look-ahead mechanism 306 to be used for the transfer, sets it to the device 20 and sets a look-ahead method to be used by the look-ahead mechanism 306 to a look-ahead method specifying register part 308. At the time of performing read access through a system bus 10, the input/ output device 20 outputs a signal for indicating the look-ahead mechanism 306 set to the device driver together with a requesting address. A look-ahead mechanism identification mechanism 304 generates a selection signal to the look-ahead mechanism 306 corresponding to the signal. Thus, the selected look- ahead mechanism 306 responds to the request. An appropriate look-ahead method is set to a free look-ahead mechanism 306 and it is utilized.
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