Adaptive replication is detailed here, including an exact definition of what is considered a "clean host": http://boinc.berkeley.edu/trac/wiki/AdaptiveReplication
At primegrid, AR is used on 3 subprojects - PPS LLR, Sophie Germain LLR and the Riesel Problem LLR. All other LLR subprojects (321, etc) do not use this. i.e. these other workunits will require wingmen before credit is granted.