U.S. stock index futures climbed on Wednesday after solid earnings and outlooks from a trio of major technology companies renewed optimism about corporate profits and the economic recovery.

Intel Corp jumped 5.6 percent to $21.11 in premarket trade after forecasting quarterly revenues well above Wall Street's estimates, easing fears the world's largest chipmaker is struggling as personal computer sales growth wanes.

Yahoo Inc advanced 4.2 percent to $16.80 after the Internet company said an important partnership with Microsoft Corp is taking longer than expected to pay off, but the company posted quarterly earnings that topped Wall Street targets.

It's not just that the earnings were good. Expectations were that we were going to begin to get a series of disappointing earnings, said Rick Meckler, president of LibertyView Capital Management in New York.

So you've got not just the reaction to the better-than-expected earnings, but a change in sentiment from what has been seen as a possibly very disappointing earnings quarter, particularly for technology.

But IBM shed 1.1 percent to $163.49 after reporting a decline in signings of new business at its global services division during the first quarter, even as its profit and revenue came in ahead of analysts' projections.

Adding to the positive tone, Spain attracted solid demand at a bond sale on Wednesday, easing concerns it could be swept up by the contagion hitting other euro zone members.

Diversified manufacturer United Technologies Corp posted a 16.9 percent rise in quarterly profit and raised its outlook for the year, boosted by strong demand for its Carrier air conditioners.

AT&T added 1.6 percent to $30.80 after the Dow component posted its first-quarter results.

S&P 500 futures added 17.7 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures gained 137 points and Nasdaq 100 futures rose 29.25 points.

Other companies scheduled to report quarterly results on Wednesday include Apple Inc , American Express Co , and Freeport-McMoRan Copper & Gold .

Apple is expected to report quarterly results tempered by caution over how supply constraints may squeeze margins and restrain iPhone and iPad sales. [nL3E7FK17N]

Economic indicators include March existing-home sales at 10 a.m..

On the M&A front, U.S. power company AES Corp said it would buy smaller rival DPL Inc for $3.5 billion in cash to expand in the Midwest by adding 500,000 retail customers in West Central Ohio.

DPL shares gained 8.8 percent to $30.01 in premarket trade.

(Reporting by Chuck Mikolajczak; Editing by Kenneth Barry)