A DMA controller transfers 32-bit words to memory using cycle stealing. The words are assembled from a device that transmits characters at a rate of 4800…
A DMA controller transfers 32-bit words to memory using cycle stealing. The words are assembled from a device that transmits characters at a rate of 4800 characters per second. The CPU is fetching and executing instructions at an average rate of one million instructions per second. By how much will the CPU be slowed down because of the DMA Transfer?
Show answerHide answer
Correct answer: (B) 0.12%
Explanation
1 character = 1 byte and a 32-bit word = 4 bytes. At 4800 characters per second, one word is assembled every 1/1200 sec, so 1200 words are transferred per second by cycle stealing. The CPU executes 1 million instructions per second, so the slowdown = (1200/1000000) × 100 = 0.12%.