# A computer has 32 words RAM with a word size of 16 bits and a cache memory of 4 Blocks with block size of 16 bits. 10m Dec2007

By | July 11, 2015

Assume a computer has 32 words RAM each having a word of 16 bits and a cache memory of 4 blocks, with each block having 16 bits. Where can we find a main memory address 21 in the cache (if it exists) if

(i) Set associative mapping is used?

(ii) Direct mapping is used?

(iii) Associative mapping is used?

Explain your answers with the help of a diagram in each case.     10

Main memory Size = 32 Words

Main Memory word size = 16 bits

Cache Memory Size = 4 Blocks

Cache Memory Block size = 16 bits

⇒1 Block of Cache = 1 Words of RAM

⇒ Total number of possible Blocks in Main Memory = 32/4 = 8 blocks

Associative Mapping:

The block can be anywhere in the cache.

Direct Mapping:

Size of Cache = 4 blocks

Location of Block 21 in Cache = 21 modulo 8 = 5

2 Way set associative mapping:

Number of blocks in a set = 2

Number of sets = Size of Cache in blocks / Number of blocks in a set

= 4 / 2 = 2

Block  21 will be located anywhere in (21 modulo 2) set, that is set 1.

(b) Construct a 4-bit right-shift register with serial input-output using D flip-flops. Describe its functioning. 5

Refer :- MCS-012 Block 1 page 77 and 78

(c) What is a micro-instruction? Explain the three micro-instruction formats, with the help of suitable diagrams.      10

Refer :- MCS-012 Block 1 page 77 and 78

(a) Explain the process of handling an interrupt that occurs during the execution of a program, with the help of an example.            9

(b) Write a program in 8086 assembly language that checks an input string against a password string stored in the memory and outputs an appropriate message if the strings are not equal. 7

(c) What is the significance of FAT? What are thelimitations of FAT 16?    4

Solved program can be found on this link http://cssimplified.com/computer-organisation-and-assembly-language-programming/what-is-the-significance-of-fat-what-are-the-limitations-of-fat-164m-jun2006

(a) What is the sequence of micro-operations required to fetch an instruction? 5

(b) Explain any five addressing modes used in an 8086 microprocessor, with the help of an example of each.      5