AMD gained 4.6% in market share while Intel ceded about 4.7%, implying that AMD has managed to steal some of their competitor's customers. That's not quite what happened.
AMD's numbers were bolstered by a jump in overall desktop processor sales, something that Intel also benefited from, but that AMD took greater advantage of with its discounted, if somewhat outdated, processors. Overall netbook processor sales were way down, mostly because big buyers have built up a sizable stock of Atoms on account of slowing sales. A decline in netbook processor sales is effectively just a decline in Atom sales; AMD still isn't a player in netbooks, and is therefore immune.
So there you have it. AMD temporarily sold cheaper desktop processors than Intel, and hardware manufacturers and resellers had plenty of Atoms for the time being. Unfortunately for AMD, that sounds an awful lot like a fluke. [PCWorld]