# A computer has 64 words RAM with a word size of 16 bits and a cache memory of 8 Blocks with block size of 32 bits. 9m Jun2008

By | August 11, 2015

Assume a computer having 64 word RAM and cache memory of 8 blocks. Where can we find memory location 25 in cache when the following are used:

(i) Direct mapping

(ii) Associative mapping

(iii) 2-way set associative (2 blocks per set) mapping

Assume 1 word – 16 bits, block size = 32 bits. 9m Jun2008

## Given:

Main memory Size = 64 Words

Main Memory word size = 16 bits

Cache Memory Size = 8 Blocks

Cache Memory Block size = 32 bits

⇒1 Block of Cache = 2 Words of RAM

⇒ Total number of possible Blocks in Main Memory = 64/2 = 32 blocks

Associative Mapping:

The block can be anywhere in the cache.

Direct Mapping:

Size of Cache = 8 blocks

Location of Block 12 in Cache = 12 modulo 8 = 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

= 8 / 2 = 4

Block 12 will be located anywhere in (12 modulo 4) set, that is set 0.

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