GATE 2012 CS (CS1) – Question 65
A computer has a 256 KB, four-way set-associative, write-back data cache, 32-byte blocks and 32-bit addresses. Every tag-directory entry includes the address tag, two valid bits, one modified bit and one replacement bit. Find tag-directory size.
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Correct answer: (A) 160 Kbits
Explanation
There are 2¹³=8192 cache lines. Each directory entry has a 16-bit tag plus 2+1+1=4 status/replacement bits, total twenty. Thus directory size is 8192×20=163840 bits=160 Kibits, option A.