Editing Cache coherence (section)

=== Directory-based ===
{{main|Directory-based cache coherence}}
: In a directory-based system, the data being shared is placed in a common directory that maintains the coherence between caches. The directory acts as a filter through which the processor must ask permission to load an entry from the primary memory to its cache. When an entry is changed, the directory either updates or invalidates the other caches with that entry.
[[Distributed shared memory]] systems mimic these mechanisms in an attempt to maintain consistency between blocks of memory in loosely coupled systems.<ref>{{cite web |title=Lecture 18: Snooping vs. Directory Based Coherency |url=https://people.eecs.berkeley.edu/~pattrsn/252F96/Lecture18.pdf |website=Berkeley.edu |access-date=14 May 2023}}</ref>