Hardware interview practice
Compare true LRU with tree PLRU
A four-way cache can use exact least-recently-used replacement or a three-bit binary-tree pseudo-LRU policy. Which statement is guaranteed?
Choose one
Answer choices
- A. Tree PLRU uses three bits and always identifies the exact least-recently-used way after every access sequence.
- B. Exact LRU and tree PLRU never update replacement state on cache hits.
- C. Tree PLRU uses three state bits but can choose a victim that is not the true least-recently-used way.
- D. Exact four-way LRU needs only two bits because there are four possible recency orders.