A directory can run short in three ways: bits per entry (how many sharers one entry can name), number of entries (how many lines it can track) and active transaction capacity. Each limit causes different behaviour. Calculate one explicitly chosen entry format before discussing overflow and replacement.
Lesson | After it you can... |
|---|---|
Extend the pilot's 4/66-bit entry to 16-1024 caches and find where each format wins. | |
Explain the Dir_i B, Dir_i NB and coarse-vector overflow rules and their invalidation cost. | |
Size a sparse directory and trace the eviction of an exclusive entry. | |
Check that every cache that may hold X stays in the candidate set across every event. |
Read in order after the pilot directory lesson and Part 5 filtering. All storage comparisons name their included fields and keep the pilot's 64-byte line size.
No. The number of allocated entries, tag width, replication, pending records and protection bits all contribute. A smaller sharer representation is only one term.