By Rex Crum, MarketWatch SAN FRANCISCO (MarketWatch) -- Tech stocks took some tentative steps forward Friday in an effort to end the week higher, with advances from National Semiconductor Corp. and other chip stocks taking the sector spotlight. The tech sector also seemed to mirror the broader market's uncertainty in the wake of an 8.9-magnitude earthquake that rattled Japan. Shares of National Semi (NSM) rose more than 4% after the chip maker's fourth-quarter revenue forecast fell in line with analysts' estimates. Late Thursday, National Semi said it expects quarterly sales of $360 million to $370 million, while analysts surveyed by Thomson Reuters had forecast revenue of $367 million. That outlook was enough to inspire investors, even though National Semi also reported third-quarter earnings of 24 cents a share on $344 million in sales. The company's profit was in line with estimates, but its sales fell short of Wall Street's $352 million forecast. Other chip stocks on the rise included Nvidia Corp. (NVDA) and Micron Technology Inc. (MU), both of which rose more than 2%. Gains also came from LSI Corp. (LSI), Texas Instruments Inc. (TXN) and Xilinx Corp. (XLNX). Despite the chip-stock gains, the Nasdaq Composite Index (RIXF) gave up 8 points to slip to 2,692. The Philadelphia Semiconductor Index (SOX) edged into positive territory. Shares of Apple Inc. (AAPL) rose 87 cents to $347.21 as the company's new iPad 2 device went on sale. Decliners included Clearwire Corp. (CLWR), which fell 4.5%. The wireless-network operator said Thursday that Chief Executive Bill Morrow and two other top executives resigned. Clearwire said Chairman John Stanton will replace Morrow on an interim basis, and promoted Chief Financial Officer Erik Prusch to chief operating officer.