WARF: P01232US

Bandwidth-Adaptive, Hybrid Cache-Coherence Protocol


David Wood, Mark Hill, Milo M. K. Martin, Daniel Sorin

The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing an adaptive hybrid protocol that improves the performance of computers with multiple processors.
OVERVIEWLarge computer software applications require computation beyond what can be provided by a single microprocessor. A popular solution to this problem is to share memory between several microprocessors. Each processor is typically provided with a cache memory into which blocks of shared memory may be loaded. The cache allows faster memory access, but must be monitored using coherence protocols to ensure that the cache’s contents accurately reflect the contents of the shared memory. Two of these coherence protocols are called “snooping” and “directory.” Because systems with more than one processor often experience varying levels of memory traffic, selecting between snooping and directory protocols results in sub-optimal performance.
THE INVENTIONUW-Madison researchers have developed an adaptive hybrid protocol that dynamically selects between a snooping-like and a directory-like protocol, allowing the system to choose the best mechanism for communicating cache coherence messages based on the bandwidth available.
  • Computers with multiple processors
  • Improves performance of computers with multiple processors
  • Outperforms snooping during periods of high bandwidth demand
  • Outperforms directory systems during periods of low bandwidth demand
  • Outperforms both snooping and directory systems during periods of intermediate bandwidth demand
For More Information About the Inventors
Contact Information
For current licensing status, please contact Emily Bauer at or 608-960-9842.
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