part 3 Cache Memory 5

Fully associative

cache structure

detailed relationships on cache address structure.

Following is the different of direct map and 8-set associative

Address Bit Partitioning


TAGINDEXOFFSET1817161514131211109876543210Compare BitsSet Select BitsByte Select Bits


 Memory size = 528KB = 2¹⁹
Block size = 32Bytes = 2⁵

Number of blocks in cache = Cache size/Block size = 64KB/32B = 2¹⁴/2⁵ = 2¹¹

Number of bits in Tag = Total bits - Index bits - Offset bits = 19-11-5 = 3

TAGINDEXOFFSET1817161514131211109876543210Compare BitsSet Select BitsByte Select Bits


The Compare Bits are compared with the corresponding Tag Bits in the Cache Directory.
The Set Select Bits are used to select a particular Set in the Cache.
The Byte Select Bits are used to select a particular byte in the accessed block.Memory size = 528KB = 2¹⁹
Block size = 32Bytes = 2⁵

Number of sets in cache = Cache size/(Set size * Block size) = 64KB/(8 blocks * 32B) = 2¹⁴/(2³ * 2⁵) = 2⁸

Number of bits in Tag = Total bits - Index bits - Offset bits = 19-8-5 = 6