Editing Bus snooping (section)

=== Write-update ===
When a processor writes on a shared cache block, all the shared copies of the other caches are updated through bus snooping. This method broadcasts a write data to all caches throughout a bus. It incurs larger bus traffic than write-invalidate protocol. That is why this method is uncommon. [[Dragon protocol|Dragon]] and [[Firefly (cache coherence protocol)|firefly]] protocols belong to this category.<ref>{{Cite book |last1=Hennessy |first1=John L |title=Computer Architecture: A Quantitative Approach |last2=Patterson |first2=David A. |publisher=Elsevier |year=2011 |isbn=978-0123838728}}</ref><ref>{{cite book |title=Computer Architecture A Quantitative Approach |last1=Patterson |first1=David A. |last2=Hennessy |first2=John L. |isbn=1-55860-069-8 |date=1990 |pages=469–471 |publisher=Morgan Kaufmann Publishers}}</ref>