Tech stocks rallied modestly Thursday, continuing a recent string of gains, this time on the back of several analyst upgrades and optimism for SanDisk's ( SNDK) foray into China.

The company was advancing 2.7% after the flash data storage cards announced it was opening its first production facility in the People's Republic of China. Shares were adding $1.43 to $55.

SanDisk is a component of the Nasdaq 100, which was 6.70 points higher to 2095.08.

GSI Group ( GSIG), which makes precision technology components such as lasers for the electronics, semiconductor, medical and other industries, was rising 10% on more optimistic third-quarter guidance. After a $6 million order from a Japanese customer, the company now expects revenue of between $82 million and $84 million and diluted earnings of 16 cents to 18 cents a share. Analysts polled by Thomson Financial expect earnings of 11 cents a share on revenue of $80.6 million. Shares were adding $1.01 to $11.16.

A flurry of analyst upgrades boosted several tech players.

Networking equipment maker Westell Technologies ( WSTL) jumped 9.2%, after Robert W. Baird upgraded the stock to outperform from neutral. Shares were rising 20 cents to $2.38.

SiRF Technologies ( SIRF), which makes chips and software to enable global positioning systems, jumped 10.9% after Credit Suisse upgraded the stock to outperform from neutral. The analyst expects a strong holiday season, according to the Associated Press. Shares gained $2.12 to $21.61.

Customer-relations management software maker Right Now Technologies ( RNOW) was adding 3.6% after RBC Capital Markets upgraded the stock to market perform from underperform. Shares were gaining 57 cents to $16.39.

Micron Technology ( MU) was gaining 6.2%, after a Lazard Capital Markets research note said it expected the chipmaker to beat Wall Street's fourth-quarter estimates, according to Reuters. Analysts polled by Thomson Financial expect a loss of 23 cents a share on revenue of $1.39 billion. Shares were up 67 cents to $11.42.

On the down side, Embarq ( EQ), which provides voice, data and Internet access to business customers, was sinking 4.2% after Merrill Lynch lowered its rating to underweight from equal weight and cut its price target to $55 from $59, according to Marketwatch. Shares were falling $2.53 to $57.24.

Advanced Micro Devices ( AMD) also was losing ground, despite no major news. The stock was down 44 cents, or 3.2%, to $13.31.