Despite an ongoing price war with arch-rival Intel, AMD managed to secure 25% of the $30-billion x86 chip market in the fourth quarter of last year. 

Reuters reports that, according to Mercury Research, AMD upped its market share to 25.3% during the period from 23.3% in the third quarter, and 21.4% for the corresponding quarter in 2005.
Intel's market share has fallen to its lowest level in 11 years. In Q4 of 2006 it was down to 74.4% from 77% in Q4 the year before.