Direction: A computer has a 256 kbyte. 4-way set associative, write back data cache with block size of 32 byte. The processor sends 32 bit addresses to the cache controller. Each cache tag directory entry contains, in addition to address tag, 2 valid bit, 1 modified bit and 1 replacement bit.
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The size of the cache tag directory is
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- 160 kbit
- 136 kbit
- 40 kbit
- 32 kbit
- 160 kbit
Correct Option: A
Number of tag bits = 16
Number of valid bits = 2
Number of modified bits = 1
Number of replacement bits = 1
Total bits in each entry = 16 + 2 + 1 + 1 = 20 bit
Each entry is attached to each cache block
Number of cache blocks are = 213
Tag directory size = Number of cache blocks × Each entry size = 213 × 20 bit = 20 × 160 bit = 160 kbit
