Problem Set A
1
.
A cache has an access time of 1 cycle. The computer with that cache experienced an average memory access time of 4 cycles, and the hit rate is 70%. What is the access time of the main memory? Did we benefit from having a cache in this system?
2
.
Research and explain a few key responsibilities of operating systems.
Given X = 01100110,
3
.
What is the value of X once you logically shift X to the right by two digits?
4
.
What is the value of X once you arithmetically shift X to the right by two digits?
Given X = 10100110,
5
.
What is the value of X once you logically shift X to the right by two digits?
6
.
What is the value of X once you arithmetically shift X to the right by two digits?
7
.
What is the value of X if you arithmetically shift it to the right by eight digits?
Perform the following number conversions:
8
.
hexadecimal value 40A5F916 to binary
9
.
binary value 11011010011010111010 to hexadecimal
10
.
Considering the arguments passed in, what does the following assembly language program do?
| Register | Use(s) |
| %rdi | Argument x |
| %rsi | Argument y |
| %rax | Return value |
| movq | %rdi, %rax |
| subq | %rsi, %rax |
| movq | %rsi, %rdx |
| subq | %rdi, %rdx |
| cmpq | %rsi, %rdi |
| cmovle | %rdx, %rax |
| ret |
11
.
Suppose that we have a system with memory access time of 8 cycles. We need to add to that system a cache with 2 cycles access time. What is the smallest hit rate needed to make that cache beneficial? (Hint: avg access time must always be an integer number not floating point.)
12
.
A cache has an access time of 1 cycle. The computer with that cache experienced an average memory access time of 4 cycles, and the hit rate is 70%. What is the access time of the main memory? Did we benefit from having a cache in this system?