* IBM slumps after quarterly results
* Apple earnings due after the close
* Futures off: Dow 102 pts, S&P 7 pts, Nasdaq 10 pts
By Chuck Mikolajczak
NEW YORK, Oct 20 (Reuters) - U.S. stock index futures were lower on Monday, following a fourth week of losses for the benchmark S&P, as quarterly results from IBM disappointed.
* IBM shares slumped 7.7 percent to $168.10 in premarket trade after the company's third-quarter earnings fell well short of Wall Street expectations. IBM had earlier said it would pay Globalfoundries $1.5 billion in cash over the next three years to take its its loss-making semiconductor unit.
* The S&P 500 rallied on Friday to pare its weekly decline, but still notched its longest stretch of weekly losses since August 2011. The S&P index is now down 6.2 percent from its record high, hurt by worries about the health of the global economy, the spread of the Ebola virus and uncertainty about the next steps for the Federal Reserve.
* Earnings season will ramp up significantly this week, with nearly 130 S&P 500 companies scheduled to report, include Apple Inc after the close on Monday.
* According to Thomson Reuters data through Friday, of 81 companies in the S&P 500 that have reported quarterly earnings, 64 percent beat analyst expectations, slightly above the 63 percent average since 1994 but below the 67 percent rate for the past four quarters.
* Third-quarter earnings are expected to grow 6.9 percent from a year ago, on revenue growth of 3.8 percent.
* European stocks fell, trimming lofty gains made in the previous session, with SAP's profit warning hitting shares in the tech sector.
* Japanese stocks led a rally in Asia, after solid U.S. data and earnings reassured investors worried about the health of the world economy.
* S&P 500 e-minis were falling 7 points, or 0.37 percent, with 239,360 contracts changing hands.
* Nasdaq 100 e-minis were down 10 points, or 0.26 percent, in volume of 31,068 contracts.
* Dow e-minis were down 102 points, or 0.63 percent, with 40,803 contracts changing hands. (Editing by Bernadette Baum)