You are in the: Small Business Computing Channelarrow View Sites +
Small Business Technology
» ECommerce-Guide | Small Business Computing | Webopedia | WinPlanet |  »Close
Enter a word for a definition... ...or choose a computer category.

   Term of the Day
   New Terms
   New Links
   Quick Reference
   Did You Know?
   Tech Support
   Webopedia Jobs
   About Us
   Link to Us

talk to us
   Submit a URL
   Suggest a Term
   Report an Error
Internet Lists
Internet News
Internet Resources
Linux/Open Source
Personal Technology
Small Business
Windows Technology
xSP Resources
Corporate Info
Tech Jobs
E-mail Offers
  Be a Commerce Partner

snooping protocol
Last modified: Thursday, September 16, 2004 

(snoop´ing prō´t&-kol´´) (n.) Also referred to as a bus-snooping protocol, a protocol for maintaining cache coherency in symmetric multiprocessing environments. In a snooping system, all caches on the bus monitor (or snoop) the bus to determine if they have a copy of the block of data that is requested on the bus. Every cache has a copy of the sharing status of every block of physical memory it has. Multiple copies of a document in a multiprocessing environment typically can be read without any coherence problems; however, a processor must have exclusive access to the bus in order to write.

There are two types of snooping protocol:

  • write-invalidate: the processor that is writing data causes copies in the caches of all other processors in the system to be rendered invalid before it changes its local copy. The local machine does this by sending an invalidation signal over the bus, which causes all of the other caches to check for a copy of the invalidated file. Once the cache copies have been invalidated, the data on the local machine can be updated until another processor requests it.
  • write-update: the processor that is writing the data broadcasts the new data over the bus (without issuing the invalidation signal). All caches that contain copies of the data are then updated. This scheme differs from write-invalidate in that it does not create only one local copy for writes.

E-mail this definition to a colleague

For pages about snooping protocol . Also check out the following links!

Related Links

related categories



Network Protocols

related terms

address bus


bus mastering


cache coherence

expansion bus

system bus

Give Us Your

Networking Hubs and Switches
snooping protocol Products

Shop by Top Models:
3Com SuperStack 3 3300 XM 24-Port Ethernet Switch (3C16985B-US)
6 store offers from $115 - $350

3Com (3C16981AN) 12-Port Ethernet Switch
4 store offers from $318 - $490

Nortel BayStack 450 Model 12T 12-Port Ethernet Switch (AL2012E15)
12 store offers from $267 - $1731

ZyXEL ES-2008 8-Port Ethernet Switch (91010002002)
6 store offers from $124 - $190

Nortel BayStack 450 Model 12F 12-Port Ethernet Switch (AL2012E19)
10 store offers from $2011 - $3964

JupiterWeb networks:

Search JupiterWeb:

Jupitermedia Corporation has two divisions: Jupiterimages andJupiterWeb

Jupitermedia Corporate Info

Legal Notices, Licensing, Reprints, & Permissions, Privacy Policy.

Web Hosting | Newsletters | Tech Jobs | Shopping | E-mail Offers