In Mexico in September 2007 Zappa won a match against Rybka by a score of 5 - 4. Many commentators had predicted a slew of draws based on the strength of the engines, but the differences in style provided an interesting match with several decisive games and many fighting draws. For some time, Zappa was considered one of the two strongest commercially available chess programs; see engine rating lists like CCRL for current rankings. Some speculate that Zappa's more efficient SMP parallel search could make it stronger on enough processors.