Gate2019 cs Q11

0. A certain processor uses a fully associative cache of size 16 kB. The cache block size is 16 bytes. Assume that the main memory is byte addressable and uses a 32-bit address. How many bits are required for the Tag and the Index fields respectively in the addresses generated by the processor?

  • Option : D
  • Explanation :
    Given cache block size is 16 bytes, so block or word offset is 4 bits. Fully associative cache of size 16 kB, so line offset should be,
    = cache size / block size
    = 16 kB / 16 B = 1 k
    = 1024
    = 10 bits Line or Index Offset
    Tag bit size would be,
    = processor address size - (line offset + word offset)
    = 32 - 10 - 4
    = 18 bits tag size
    Since, there no option matches, but if we assume that Line Offset is a part of Tag bits, therefore,
    Tag bits = 18+10 = 28 bits
    Line or Index offset = 0 bits (since fully associative cache memory),
    Word or block offset = 4 bits
    32 - bit
    Tag offsetWord offset
    28 bit4 bit
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