JAN 2001

Question Paper of CS-12 – Computer Architecture of Jan 2001 from IGNOU

Note : Question one is compulsory. Answer any three from the rest.

1(i) The execution times (in seconds) of four programs on three computers are given below:

Execution Time (in seconds)
Program Computer A Computer B Computer C
P1 1 10 20
P2 1000 100 40
P3 500 1000 50
P4 100 500 100

Assume that 100,000,000 instructions were executed in each of the four programs. Calculate the MIPS rating of each program on each of the three machines. Based on these ratings. Can you draw a clear conclusion regarding the relative performance of the three computers?

(ii) Answer the following questions:
(a) What causes a processor pipeline to be underpipelined?
(b) What are the factors limiting the degree of superscalar design?
(c) Compare the instruction set architecture in RISC and CISC processors in terms of instruction formats and addressing modes.
(d) Factors affecting cache hit ratio.

2 Compare the relative merits of the three cache memory organizations:

(i) Fully-associative cache
(ii) Set-associative cache
(iii) Sector mapping cache

3. Answer the following questions on designing scalar RISC or Superscalar RISC processors: [15]

(i) Why do most RISC integer units use 32 general-purpose registers?

(ii) What are the design tradeoffs between a large register file and a large D-cache?

(iii) Explain the relationship between the integer unit and floating point unit in most RISC processors with scalar or superscalar organization.

4. Answer the following questions on pipelining and superscalar techniques:

(i) Speed-up factors and the optimal number of pipeline stages for a linear pipeline unit.

(ii) Mechanisms for instruction pipelining. ]

5. Explain the following as applied to multiprocessors and multicomputers:

Buffering flow control using virtual cut through routing
Blocking flow control in warm hole routing
Virtual networks and sub networks

6. Distinguish among the following vector processing machines in terms of architecture and performance range:

(i) Full scale vector supercomputers
(ii) High-end mainframes or near supercomputers
(iii) Minisupercomputers or supercomputing workstations

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