# Draw a diagram address mapping of RAM & Cache – IGNOU MCA Assignment 2015 – 16

By | August 29, 2015

MASTER OF COMPUTER APPLICATIONS

Course Code : MCS-012
Course Title : Computer Organisation and Assembly Language Programming
Assignment Number : MCA(I)/012/Assignment/15-16
Maximum Marks : 100
Weightage : 25%

A computer has 1MB RAM and has word size of 16 bits. It has cache memory having 16 blocks with a block size of 32 bits. Explain how a main memory address will be mapped to a cache address, if

(i) Direct cache mapping is used

(ii) Associative cache mapping is used

(iii) Two way set associative mapping scheme is used.

## Given:

Main memory Size = 1 MB (RAM)

Convert it to Words if word size is 16 bits

Main memory Size = 65536 Words

Main Memory word size = 16 bits

Cache Memory Size = 16 Blocks

Cache Memory Block size = 32 bits

⇒1 Block of Cache = 2 Words of RAM

⇒ Total number of possible Blocks in Main Memory = 65536 /2 = 32768 blocks

Associative Mapping:

The block can be anywhere in the cache.

Direct Mapping:

Size of Cache = 16 blocks

Location of Block 260 in Cache = 260 modulo 16 = 4

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

= 32768  / 2 = 16384

Block 260 will be located anywhere in (260 modulo 8) set, that is set 4.