A CPU generates 32 bits virtual addresses. The page size is 4 KB. The processor has a translation look-aside buffer (TLB) which can hold a total of 128-page table entries and is 4- way set associate. The minimum size of the TLB tag is

TLB Tag Size Calculation

Given:

• Virtual Address = 32 bits
• Page Size = 4 KB = \(2^{12}\) → Offset = 12 bits
• VPN = 32 − 12 = 20 bits
• TLB entries = 128, 4-way set associative → 32 sets

Set index bits: \( \log_2(32) = 5 \text{ bits} \)

TLB Tag = VPN − Set Index = 20 − 5 = 15 bits

✅ Final Answer: 15 bits