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CS501 Assignment No 4 Spring 2012 solution

Assume that three I/O devices are connected to a 16-bit 100 MIPS CPU. The first device is a hard drive with a maximum transfer rate of 2MB/sec. It has a half word (16-bit) bus. The second device is a floppy drive with a transfer rate of 10KB/sec over 8-bit bus, and the third device is a keyboard that must be polled 25 times per second. Assuming that the polling operation requires 40 instructions for each I/O device, determine the percentage of CPU time required to poll each device and also state what you infer after calculating these percentages
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Solution:

1024 x 2^10 x 40=41943040
(5.12*10^6)/(100*10^6)=5012%

for floppy
10*2^10*40=409600
(0.256*10^6)/100*10^6)=0.256%

for keyboard
25*40=1000

 

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