By Rex Crum, MarketWatch

SAN FRANCISCO (MarketWatch) -- A rare analyst upgrade of Dell Inc. gave the troubled PC company a big boost in Monday's trading session, as tech stocks on the whole began with the week in positive territory.

Dell (DELL) rose 74 cents a share, or almost 8%, to $10.38 after Goldman Sachs analyst Bill Shope raised his rating on Dell's stock to buy from sell, with a price target of $13 a share. In a research note, Shope said that while demand for PCs remains down, "we could begin to see sentiment and expectations tilt positively in 2013."

Shope added that Wall Street's consensus earnings expectations for Dell's next fiscal year are also down so much that, "We believe this reset has produced a positive risk-reward (opportunity) for the stock."

Apple Inc. (AAPL) shares rose 1%, to $591.50, after the company said the iPhone 5 would be available in South Korea on Friday, in China next week, and in more than 50 other countries before Christmas.

Chipmaker Advanced Micro Devices Inc. (AMD) was up more than 7%, at $2.35 a share, and online review and recommendation company Yelp Inc. (YELP) saw its shares rise more than 5%, to $9.89.

Facebook Inc. (FB) shares rose almost 3%, to $28.77, following reports that the company was in talks to acquire WhatsApp, a cross-platform mobile-messaging application developer.

Zynga Inc. (ZNGA) shares lost more ground, falling almost 6%, to $2.32 a share in wake of the social-gaming company announcing a series of changes in its partnership with Facebook. There were also reports of more executives leaving the company.

Internet radio company Pandora Media Inc. (P) rose 1.3%, to $8.84 a day ahead of its next quarter earnings report.

Research In Motion Ltd. (RIMM) edged into positive territory, to reach $11.64, despite a rating downgrade by Canaccord Genuity analyst Michael Walkley, who cut the BlackBerry maker to see from hold.

Walkley said that despite the recent rise in RIM's share price ahead of the launch of the BlackBerry 10 operating system next year, "our checks and analysis of the global competitive landscape suggest a very low probability BlackBerry 10 sales can turn around RIM's long-term business trends."

The Nasdaq Composite Index (RIXF) rose 5 points to 3,015, while the Philadelphia Semiconductor Index (SOX) and the Morgan Stanley High Tech 35 Index managed small gains.

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