From late fall 1996 through early summer 1997, Mark Tuttle, Yuan Yu, and I worked on the specification and verification of the cache-coherence protocol for a computer code-named Wildfire. We worked closely with Madhu Sharma, one of Wildfire’s designers. We wrote a detailed specification of the protocol as well as a specification of the memory model that it was supposed to implement. We then proved various properties, but did not attempt a complete proof. In early 2000, Madhu, Mark, and I wrote a specification of a higher-level abstract version of the protocol.

There was one detail of the protocol that struck me as particularly subtle. I had the idea of publishing an incorrect version of the specification with that detail omitted as a challenge problem for the verification community. I did that and put it on the Web in June, 2000. To further disseminate the problem, we wrote this description of it for the CAV (Computer Aided Verification) conference.