WBUT Question Papers CS Advanced Computer Architecture B Tech – 2009

WBUT Question Papers CS

 Advanced Computer Architecture B Tech – 2009

Time : 3 Hours J

Full Marks : 70

GROUP-A (Multiple Choice Type Questions )

  1.                                                                                                                                                                                                                                                                           Choose the correct alternatives for the following :                 10 x 1 = 10

1) The vector stride value Is required

a) to deal with the length of vectors
b) to find the parallelism in vectors
c) to access the elements in multi-dimensional vectors
d) to execute vector instruction.
The performance of a pipelined processor suffers if
a) the pipeline stages have different delays
b) consecutive instructions are dependent on each other
c) the pipeline stages share hardware resources
d) all of these.


111) Consider the cache memory with access time 40 ns has the hit ratio of 80%. The regular memory has an access time of 100 ns. What is the effective access time for CPU to access memory ?

a)         52 ns                     b) 60 ns

c)      70 ns                     d) 80 ns.

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CS/B.TECH (C8E)/SEM-t/CS-i03/09                                  4

iv)            What Is a main advantage of classical vector systems ( VS ) compared to RISC based systems ( RS ) ?

a)               VS have significantly higher memory bandwidth than RS

b)               VS have higher clock rate than RS

c)               VS are more parallel than RS

d) None of these.                                  1 I

v)              Associative memory Is


a)               pointer addressable memory

b)               very cheap memory

c)                content addressable memory

d)               slow memory.                                                                                                                                               I 1

vi)            The principle of locality justifies the use of

a) interrupts                                                              b) polling .

c) DMA                                                                         d) cache memory………………………………………….. 1        – , I

vll) How many address bits are required for a 512 x 4 memory ?

a)      512           b) 4

c)    9                 d) Aq-Aq. I- 1

vill) The division of stages of a pipeline Into sub-stages is the basis for *

a)               pipelining

b)                super-pipelining

c)                superscalar

d)               VLIW processor.                                 ___

ix)             What will be the speed up for a four stage linear pipeline when the number , of instruction re * 64 ?

a)          4*5

. c) 6-5

x)               Dynamic pipeline allows

a)               multiple function to evaluate                                     >

b)               only streamline connection

c)               perform fixed function

d)               none of these.                                                                                                                                        L.-—J

GROUP-B (jlhort AnswerType Questions )

Answer any three of the following questions.    3 *5 ■ 18 2.    Consider the pipelined execution of these instructions :

DADD            Rl, J12, R3

DSUB            R4, Rl, R5

AND              R6, R1.R7

OR              R8.R1.R9

XOR             RIO, R1.R11

Explain how the above execution may generate a data hazard and describe a way to minimize the data hazard stalls using forwarding. Modify the above example to show a case where forwarding may not work.


  1. 3.              Consider a computer where the clock per Instruction ( CPI ) is 10 when all memory accesses hit ( no memory stalls ) in the cache. Assume each clock cycle is 2 ns. The only data accesses are loads and stores, and these total 50% of the instructions. * ■ ‘ ‘ ‘ ‘ .

Assume the following formula for calculating execution time :

CPU execution time * ( CPU clock cycles + Memory stall cycles ) x Clock cycle time.

For a program consisting of 100 instructions :

  • Calculate the CPU execution time assuming there are no misses.

. • . . *

  • Calculate the CPU execution time considering the miss penalty Is 25 clock cycles and the miss rate is 2%.

Discuss the difference between write through and write back cache policies.

  1. 4.      Assume the performance of 1 -word wide primary memory organization is

*               4 clock cycles to send the address

  • 56 clock cycles for the access time per word

*               4 clock cycles to send a word of data

Given a cache block of 4 words, and that a word is 8 bytes, calculate the miss penalty and tiie effective memory bandwidth.

Re-compute the miss penalty and the memory bandwidth assuming we have

*               Main memory width of 2 words

*               Main memory width of 4 words

  • Interleaved main memory with 4 banks with each bank 1 -word wide.
  1. 5.              Explain the concept of .strip mining used in vector processors. Why do vector processors use memory banks ?
  2. 6.              Discuss Flynn’s classification of parallel computers.

ii84i mum’x t                ■

GROUP -C ( Long Answer Type Questions )

Answer any three of the following questions.                             3×15 = 45

  1. 7.              a) Design an arithmetic unit with variable S and 2 n-blt data Inputs A and B. The circuit generates following arithmetic operations In conjuctlon with carry In Cta.
Draw the logic diagram.


cta = 0





D = A + B

D = A – 1


D = A- 1

D = A + B’ + 1


b)         What is floating point arithmetic operation ? Explain all ( addition, difference, multiplication, division ) operations with example.

c)          What are logical address and physical address ? If segment no. la 8. page no. is 04, word no. Is 40. Segment no. 8 hold 30 and page no. 30 hold 019, what will be corresponding physical address ? For answer figure Is essential.                                                                              5 + 5 + 5

  1. 8.              a) What Is I/O Interface ?

b)         What are I/O us. Memory Bus and Isolated us. Memory-Mapped I/O ?

c)          What are the different mechanisms of Asynchronous Data Transfer ? Explain In brief.

d)         Explain DMA working principle.                                                                     2 + 3 + 5 + 5

  1. 9.              a) What are the different pipeline hazards and what are the remedies ?

b)         What Is Vector array processor ? Explain with example.

c> Describe Harvard architecture.                                                                                 5 + 5 + 5

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  1. 10.         a) Apply Booth’s algorithm to multiply the two numbers +11 and -12.
  2. What -is the limitation of direct mapping method ? Explain with example how it

can be Improved in set-associative mapping.

c)                Use 8-bit 2’s complement integer to perform – 43 + (- 13 ).

d)               What is a tri-state buffer ? Design a common bus system using tri-state buffers for two registers of 4-bits each.

e) What is serial adder ? Discuss it briefly with diagram.   3 + 4 + 3 +3 + 2

  1. 11.         a) What are the different methods for control unit design ? Explain.

b)               Write down the different addressing modes with examples.   ‘

c)               t What do you mean by pipeline processing ?

d)               What are instruction pipeline and arithmetic pipeline ?

e)  Find 2’s complement of (1 AB)16 represented in 16 bit format. 4 + 6+ 2 +2 + 1



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