# Advanced Computer Architecture December 2010

Note: Answer any FIVE full questions, selecting at least TWO questions from each part.

PART-A

1 . List and explain four important technologies, which have led to the improvements in computer System.

 Component Product Performance Power Processor Sun Niagara 8-core 1.2 cm 72-79 W DRAM Kingston 1 GB 184 – pin 3,7 W Hard drive . Diamond Max 7200 rpm 7,9 W read 4.0 Wr idle

i)    Assuming the maximum load for each component, a power supply efficiency of 70%, what wattage must the server’s power supply deliver to a system with a Sun Niagara 8-oore chip,2 GB 1.84-pin. Kingston DRAM and 7200 rpm hard drives?

ii)   How much powrer will the 7200 rpm disk drive consume, if it is idle roughly 40% of me lime?

iii)  Assume that for the same set of requests, a 5400 rpm disk will require twice as much time to read data as a 10800 rpm disk. What percentage of time would the 5400 rpm disk drive be idle to perform the same transaction as in pari  (ii)?

c.  We will run two applications on dual Pentium processor, but the resource requirements are not the same. The first application needs 80% of the resources, and the other only 20% of the resources,

i)    Given that 40% of the first application is parallelizable, how much speed up will we achieve with that application, if run in isolation?

ii)   Given that 99% of the second application is parallelizable, how much speed up will this application observe, if run in isolation?

iii)  Given that 40% of the first application is parallelizable, how much overall system speedup would you observe, if we parallelized it?

2 a .List pipeline hazards, Explain any one In detail.

b.  List and explain five different ways of classifying exception in a computer system.

c.   An unpipelined machine has 10 ns clock cycle and it uses four cycles for ALU operations and branches, five cycles for memory operations. Assume that relative frequencies of these operations are 40%, 20% and 40% respectively, Suppose due to clock skew and set up, pipelining the machine adds 1 ns overhead to the clock. Find the speed up from pipelining,

3 a. Show how the below loop would look on MIPS 5-stage pipeline, under the following situations. Find the number of cycles per iteration, for each case. Assume the latencies for integer and floating point operations, as given in the prescribed text book.

Loop: L . D F0, 0 R1)

ADD , D F4, F0, F2 S.D F4,0(RI)

DADDUI RI, Rl, # – 8 BNE RI,R2, loop

i)                   Without scheduling and without loop unrolling.

ii)                 With scheduling and without loop unrolling.

iii)               With loop unrolling four times and without scheduling.

iv)               With loop unrolling four times and with scheduling.

v)                 b. What is the drawback of 1-bit dynamic branch prediction method? Clearly state, how it is overcome in 2-bit prediction. Give the state transition diagram of 2-bit predictor. (08 Marks)

4 a. Explain the salient features of VLIW processor.

b. Explain branch-target buffer.

c. Write a short note on value predictors.

PART-B

5 a. What is multiprocessor cache coherence? List two approaches to cache coherence protocol. Give the state diagram for write-invalidate write-back cache coherence protocol. Explain the three states of a block.

b. List and explain any three hardware primitives to implement synchronization.

6 a. Assume we have a computer where CPI is 1.0 when all memory accesses hit in the cache. The only data accesses are loads and stores, and these total 50% of the instructions. If the miss penalty is 25 cycles and miss rate is 2%, hour much faster would the computer be, if all instructions were cache hits?

b. Briefly explain four basic cache optimization methods.

7 a. List and explain three C’s model that sorts all cache misses.

b. Explain the optimization methods mentioned below :

i) Trace cache to reduce hit time

ii) Non-blocking cache to increase cache bandwidth

in) Multi banked cache to increase cacncoanu width.

c.   Briefly explain how memory protection is enforced via virtuaI memory.

8 a. Consider the loop below;

for (i – 1 ; i < 100 ; i = i + 1) {

A[i] = A[i] + B[i];l * SI *1 B[i+lJ=C[i] + D[i];I*S2*l }

What are the dependences between Si and S2? Is this loop parallel? If not, show how to make it parallel.

b. Explain Intel IA-64 architecture.

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