SAN FRANCISCO -- Investors had two reasons to stick with Sirf Technology ( SIRF) as the chipmaker floundered: a takeover or a turnaround.

Both of those hopes evaporated with last week's legal ruling against Sirf.

The preliminary finding by a U.S. International Trade Commission judge that Sirf is infringing on six of Broadcom's ( BRCM) patents represents more than the latest in a string of bad news for Sirf -- it marks the end of any reason to care about a company that once seemed poised to be a central player in a new world of iPhone-like gadgets.

Shares of Sirf plunged 24% to $2.44 Monday as news of the ITC ruling spread.

Sirf developed -- and once ruled -- the market for GPS chips that communicate with overhead satellites to provide an electronic device with its precise geographic location.

But a rush of competitors has eroded the price of Sirf's GPS chips and its market share.

According to iSuppli, an industry research firm, Sirf had more than a 90% share of the market for GPS chips in cell phones in 2006. In the first quarter of 2008, Sirf's share had dwindled to 36%, while Texas Instruments ( TXN) had grabbed 35% and Infineon ( IFX) had 21%.

In the market for portable navigation devices -- a larger market for Sirf than cell phones -- competition has also been fierce with chipmakers Broadcom and ST Microelectronics ( STM)stealing significant share from Sirf at customers like Garmin ( GRMN) and TomTom, according to RBC Capital Markets analyst Mahesh Sanganeria.

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