SiRF ( SIRF) dropped 7% late Thursday after the chip outfit posted a soft fourth quarter.

For its fourth quarter ended Dec. 31, the San Jose, Calif., company earned a tax benefit-aided $17 million, or 33 cents a share. That's up from the year-ago $2.8 million, or 7 cents a share.

But excluding unusual items such as the tax benefit, latest-quarter earnings fell to a dime a share from 15 cents a year ago, leaving SiRF a penny shy of the Thomson First Call analyst estimate. Revenue was similarly weak, inching up 5% from a year ago to $27.5 million, which is $2 million shy of the Wall Street consensus.

"Revenue performance in Q4 was affected by delays in the production release of SiRFStar III software and by a shortfall in IP revenue," CEO Michael Canning said. "Now that SiRFStar III software has been fully released to customers, our design win momentum and other key metrics continue very strong and augur well for the future."

SiRF slipped 79 cents after hours to $10.