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US STOCKS-Wall St slips on weak results, but Boeing rallies

* Caterpillar falls after results, chipmakers also drop

* Boeing rise curbs Dow's decline on higher full-year outlook

* China may tighten cash supply to address inflation risks

* Indexes off: Dow 0.5 pct, S&P 0.5 pct, Nasdaq 0.6 pct

By Ryan Vlastelica

NEW YORK, Oct 23 (Reuters) - U.S. stocks fell on Wednesday as shares of Caterpillar and a number of chipmakers tumbled in the wake of results, putting the S&P 500 on track to snap a four-session streak of record highs.

The earnings of two Dow components underlined how mixed the corporate reporting season has been, with investors concerned about revenue growth and company forecasts.

Caterpillar Inc was one of the biggest decliners on the S&P, slumping 6 percent to $83.83 after the heavy-equipment machinery maker cut its full-year outlook for a third time and its profit missed expectations. That sent shares tumbling by their most in a day since September 2011.

On the upside, Boeing Co surged 4.1 percent to $127.50 after reporting a rise in adjusted profit and raising its full-year forecast.

"We've seen a mixed bag as far as earnings go, and comparisons will only get harder next quarter," said Jerry Villella, investment specialist for JP Morgan Private Bank in Dallas. "You have to be more careful about where you invest. We have more modest expectations going forward."

About a third of S&P 500 companies have reported thus far, with 66.3 percent topping profit expectations, a rate that is slightly higher than the historical average. Roughly 54 percent have beaten on revenue, below the 61 percent long-term average.

Villella, who helps oversee about $935 billion in assets, said some sectors, like financials, were proving to be strong, "though technology is a bifurcated story."

Semiconductor stocks dropped 3 percent a day after Broadcom, Altera and RF Micro Devices joined Intel and Texas Instruments on a list of semiconductor companies that have unveiled underwhelming quarterly forecasts this past week.

Broadcom shares fell 1.6 percent to $26.72, Altera lost 13 percent to $32.52 and RF Micro lost 8.3 percent to $5.65.

The Dow Jones industrial average was down 68.99 points, or 0.45 percent, at 15,398.67. The Standard & Poor's 500 Index was down 9.14 points, or 0.52 percent, at 1,745.53. The Nasdaq Composite Index was down 25.14 points, or 0.64 percent, at 3,904.43.

The S&P 500 closed at an all-time high on Tuesday, its fourth straight record. Its 23 percent gain on the year to Tuesday was just shy of its 23.5 percent advance in 2009, the index's best year over the past decade.

Global equity markets weakened Wednesday as China's primary short-term money rates rose on concerns the People's Bank of China may tighten its cash supply to address inflation risks, which could hurt growth in the world's second-largest economy. Shanghai shares fell 1.3 percent.

Further hurting sentiment, the European Central Bank said it would put top euro zone banks through rigorous tests next year to build confidence in the sector. Some analysts said that if the review reveals unexpectedly large problems, investor confidence could be undermined.

The S&P financial sector index fell 0.8 percent. Among the European banks traded on U.S. exchanges, Barclays Plc fell 2.1 percent to $17.34 and Deutsche Bank lost 1.8 percent to $49.48.

A unit of Samsung Electronics could become the biggest shareholder of Corning Inc, the maker of scratch-resistant Gorilla Glass used in many mobile gadgets. Corning shares jumped 12 percent to $17.22.

Shares of Cree Inc fell 15 percent to $63.25 after the maker of light-emitting diodes forecast current-quarter earnings below analysts' estimates.