[理工] [計組]-I/O

看板Grad-ProbAsk作者killerjoe (寂寞邊界)時間16年前 (2010/01/07 00:57)推噓4(4推 0噓 9→)

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題目 Assume that the initial setup of a DMA transfer takes 1000 clock cycles for the processor,and assume the handling of the interrupt at DMA completion requires 500 clock cycles for the processor.The hard disk has a transfer rate of 4MB/sec and uses DMA.If the average transfer from the disk is 8KB ,what fraction of the 500MHz processor is consumed if the disk is actively transferring 100% of the time?Ignore any impact from bus contention between the proceesor and DMA controller. 答案 (1)每次DMA傳送所花費的時間=8KB/(4MB/sec)=2 * 10^-3 sec ((1000+500)clock/次) (2)硬碟每秒所花費的時clock cycle = --------------------- =750*10^3 clock/sec 2 * 10^-3 sec/次為什麼可以拿 DMA的setup time+handling interrup time來除以DMA傳送時間呢? -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 114.42.215.32

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converse2006

01/07 01:37, , 1^F

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converse2006

01/07 01:38, , 2^F

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killerjoe

01/07 01:47, , 3^F

01/07 01:47, 3^F