Q.5. I/O Issues [25 marks]
1. Suppose your system's daytime processing load consists of 60+g% CPU activity and 40-g%
disk activity. After doing some research, you have learned that you can upgrade your disks
for $8,000 to make them 2.5 times as fast as they are currently. You have also learned that
you can upgrade your CPU to make it 1.4 as fast for $5,000.
a) Which upgrade would you choose to yield the best performance improvement for the
least cost?
b) Which upgrade would you choose if you don't care about the money, but want a faster
system?
c) What is the break-even point for the upgrades?
Answer
1.
what should be the new CPU price (keeping the old disk price), so that the cost per
1% performance increase would be the same for both upgrades?
2.
what should be the new Disk price (keeping the old CPU price), so that the cost per
1% performance increase would be the same for both upgrades?
Answer
2. Suppose a disk drive has the following characteristics:
• 6+f surfaces
• 16,383 tracks per surface
• 63 sectors per track
• 512 B/sector
• Seek time of 8.5 + g milliseconds
• Rotational speed of 7,200 RPM
• Transfer rate of 3 MB/s
a) What is the capacity of the drive?
b) What is the disk access time?
Answer
