By Benjamin Pimentel

The tech sector sank Wednesday afternoon, weighed down by shares of Yahoo Inc., which plunged more than 10% on news of a long-discussed search deal with Microsoft Corp.

Yahoo (YHOO) fell 11.5% to about $15.23 after the two tech bellwethers unveiled a 10-year search agreement following a bitter battle over Microsoft's failed bid to buy the Web portal for roughly $47 billion.

"Big victory for Microsoft, which gets what it wanted for no up-front payment," analyst Roger Kay of Endpoint Technologies Associates said. "The earlier deal would have been much better for Yahoo. No up-front payment is vastly different from $47 billion in the bank."

Microsoft (MSFT) was up a fraction, surviving a sector-wide sell-off that pulled the Nasdaq Composite Index (RIXF) down by 0.8% to 1,959. The tech-heavy index is down a fraction for the week.

The Microsoft-Yahoo deal was widely perceived as a threat to Google Inc. (GOOG), whose shares were down about 1%.

But Kay also said: "I wouldn't be quaking in my boots if I were Google," adding that the Microsoft-Yahoo alliance "has a long way to go to prove it can take even a single point of share from Google."

The tech sector also took a hit from declines in semiconductor shares as the Philadelphia Semiconductor Index (SOX) lost 1.5%, with major chip makers falling, including Advanced Micro Devices Inc. (AMD), Intel Corp. (INTC) and SanDisk Corp. (SNDK)

Other major tech names were also in the red, including Cisco Systems Inc. (CSCO), Dell Inc. (DELL) and eBay Inc. (EBAY)

Shares of disk-drive maker Western Digital Corp. (WDC) were down 2.4% at $30.06 after the company reported its own results for the fourth fiscal quarter. Net earnings slipped nearly 9% for the period.