Question

A 4-way set-associative cache memory unit with a capacity of 16 KB is built using a block
size of 8 words. The word length is 32 bits. The size of the physical address space is 4 GB.
The number of bits for the TAG field is _____

Answer 1

Answer on Question #45245 – Engineering - Other

A 4-way set-associative cache memory unit with a capacity of 16 KB is built using a block size of 8 words. The word length is 32 bits. The size of the physical address space is 4 GB. The number of bits for the TAG field is

Solution

Physical address size = 32 bits.

Cache size = 16k bytes = $2^{14}$ Bytes.

Block size = 8 words = 8 · 4 Byte = 32 Bytes (where each word = 4 Bytes).

No. of blocks = $\frac{2^{14}}{2^5} = 2^9$.

Block offset = 9 bits.

No. of sets = $\frac{2^9}{4} = 2^7$.

Set offset = 7 bits

Byte offset = 8 · 4 Bytes = 32 Bytes = $2^5$ = 5 bits.

$$TAG = 32 - (7 + 5) = 20 \text{ bits}.$$

Answer: 20 bits.

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