※ 引述《dendrobium (石斛蘭)》之銘言：
: 1. An I/O device whose maximum bandwidth is 100,000 bits/sec is connected to
: a computer system. The I/O controller interrupts the CPU whenever it receives
: a byte. The interrupt handling routine consists of 100 instructions. The CPU
: executes 10 million instructions per second on the average. What percentage
: of the CPU's time is used to serve the I/O device, asuming that the device
: transmits data with the maximum speed?
: (a)1.25% (b)2.5% (c)12.5% (d)25%
因為 I/O 頻寬是每秒 10萬 bits，所以 100000 / 8 為每秒可傳的 bytes
而第二行說到，每收到一個 bytes 就會執行 I/O controller interrupt
而 I/O controller interrupt 包含 100 個指令。
=> { ( 100000 / 8 ) * 100 } / 10 * 10^6 = 0.00125 * 100 = 0.125 = 12.5%
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