COSC 3332 HW5

Question 1

Suppose the daytime processing load consists of 60% CPU activity and 40% disk activity. Your customers are complaining that the system is slow. After doing some research, you learn 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 times as fast for $5,000.

• Which would you choose to yield the best performance improvement for the least amount of money?
• Which option would you choose if you dont care about the money, but want a faster system?
• What is the break-even point for the updates? That is, what price would we need to charge for the CPU (or the disk change only one) so the result was the same cost per 1% increase for both?

Question 2

Suppose a disk drive has the following characteristics:

• 5 surfaces
• 1,024 tracks per surface
• 256 sector s per track
• 512 bytes/sector
• Track-to-track seek time of 8ms
• Rotational speed of 7,500 rpm

What is the capacity of the drive?

What is the access time?

Is this disk faster than the one described in exercise 28? Explain. (4 surfaces, 1,024 tracks per surface, 128 sectors per track, track-to- track seek time of 5ms, 512 bytes/sector, rotational speed of 5,000 rpm).

Question 3

What are the advantages and disadvantages of having a small number of sectors per disk cluster? (hint: you may want to think about retrieval time and the required life-time of the archives.)

Question 4

What is the difference between multiprogramming and multiprocessing? Multiprocessing and multithreading?

Question 5

Discuss the following questions relative to compilers:

• Which phase of a compiler would give you a syntax error?
• Which phase complains about undefined variables?
• If you try to add an integer to a character string, which compiler phase would emit the error message?

Question 6

Why the execution environment of a Java class is called a virtual machine? How does this virtual machine compare to a real machine running code written in C?