题目内容

I/O系统主要有三种方式来与主机交换数据,其中主要用软件方法来实现,CPU的效率低的是 (1) ;要有硬件和软件两部分来实现,它利用专门的电路向CPU中的控制器发出 I/O服务请求,控制器则 (2) 转入执行相应的服务程序的是 (3) ;主要由硬件来实现,此时高速外设和内存之间进行数据交换 (4) 的是 (5) 。供选择的答案 4()

A. 通过CPU的控制,利用系统总线
B. 不通过CPU的控制,利用系统总线
C. 通过CPU的控制,不利用系统总线
D. 不通过CPU的控制,不利用系统总线

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