In an instruction execution pipeline, the earliest that the data TLB…
2008
In an instruction execution pipeline, the earliest that the data TLB (Translation Lookaside Buffer) can be accessed is
Answer: C. after effective address calculation has completed — Answer: The earliest the data TLB can be accessed is after the effective address calculation has completed. Reasoning: Effective address calculation produces…
- A.
before effective address calculation has started
- B.
during effective address calculation
- C.
after effective address calculation has completed
- D.
after data cache lookup has completed
Attempted by 98 students.
Show answer & explanation
Correct answer: C
Answer: The earliest the data TLB can be accessed is after the effective address calculation has completed.
Reasoning:
Effective address calculation produces the virtual address that the TLB must translate.
The TLB performs virtual-to-physical translation, so it cannot perform a meaningful translation before the virtual address exists.
After translation, the physical address is used for the data cache lookup (or for tag checks in physically-tagged caches). While some designs may overlap parts of address generation, translation, and cache indexing to reduce latency, the logical earliest point for accessing the TLB is once the effective address is available.
Conclusion: The TLB access must follow completion of effective address calculation, because translation needs the computed virtual address.