Hitachi, Ltd.

Yasuo Minowa

Nagaharu Hamada

Toshitaka Hara

A computer system comprises a central processor unit, a single memory apparatus and an external processor unit which is adapted to read out N bytes of data in each period of T.sub.o. The number n of data remaining to be processed after a time elapse T.sub.1 (T.sub.1 &lt; T.sub.o) from the beginning of the period T.sub.o is successively compared with the number m of data which can be read out continuously by the external processor unit during a remaining time span (T.sub.o -T.sub.1). So long as the number n is smaller than the number m the external processor unit is allowed to read out the data from the memory apparatus only when the central processor unit is not using the memory apparatus. On the other hand, when the number n becomes equal to the number m, connection between the memory apparatus and the central unit is interrupted to allow in turn the external processor unit to read out data from the memory apparatus, whereby the processing efficiency of the computer system is improved.

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Higashimurayama, Japan

Yasuo Minowa