V22.0436 - Prof. Grishman
Practice Final Exam Questions (1): Performance Issues
- A processor runs at 100 Mhz. What is the length of its clock
- A disk has an access time of 10 ms. Assuming the time for
data transfer is negligible, how many disk accesses can be performed
- Suppose that when program Zippo runs, it executes 200,000
loads, 100,000 stores, 699,998 R-type instructions, and 2 multiply
instructions. Consider 2 machine designs: in design M1, the
clock rate is 100Mhz; loads and stores take 2 cycles, R-type
instructions take 1 cycle, and multiplies take 5 cycles. In design
M2, the clock rate is 66Mhz and all instructions take 1 cycle.
Which machine is faster?
- Consider two alternative caches, each of which has a capacity
of 8 words and a block size of one word. Cache D is a direct
mapped cache, and cache T is a two-way set associative cache.
Suppose the cache is initially empty and we fetch the words at
the following addresses in sequence: 1, 2, 9, 3, 1, 5, 9. Which
of these fetches will result in cache hits?
- Suppose that we have a 10 ns cache (it takes 10 ns to access
the data or identify a miss), and a memory system with a 100 ns
access time. What is the average memory access time if the cache
hit rate is 97%? If we built a larger cache, with a 12 ns access
time but a hit rate of 98%, would the average memory access time
increase or decrease?
- Suppose we have a floppy disk which transfers 50 KB and interrupts
the CPU each time a byte is available. The CPU executes approximately
50 mips, and the interrupt routine takes 25 instructions to transfer
a byte to memory. What fraction of the CPU time will be occupied
doing IO with the floppy disk?