U.S. stock index futures rose on Wednesday as investors awaited congressional testimony from Federal Reserve Chairman Ben Bernanke for clues to the U.S. central bank's thinking on the economy.

Bernanke will give semiannual testimony on monetary policy and the state of the economy before the U.S. House Financial Services Committee. Investors wonder if a surprise hike in the discount rate last week could presage a rise in interest rates.

Dave Rovelli, a trader at Canaccord Adams in New York, said investors are concerned that an end to Fed purchases of mortgage-backed securities (MBS) could push mortgage rates up and kill off a recovery in the housing market.

They want to see how he's going to go on ending his MBS buyback and what's his view on the discount rate, he said.

S&P 500 futures were up 1.4 points and 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 rose 15 point, and Nasdaq 100 futures added 4.5 points.

Shares in Autodesk Inc gained 7.2 percent to $27.50 in premarket trade after the architectural software company posted better-than-expected quarterly results late Tuesday.

On the economic front, the Commerce Dept is to release new home sales for January. Economists surveyed by Reuters forecast a total 360,000 annualized units in the month, compared with 342,000 in December.

In one positive sign from the housing market, U.S. luxury homebuilder Toll Brothers Inc posted a narrower-than-expected quarterly loss and said it sees improvement in the beleaguered sector. The shares rose 3.2 percent to $19.51 premarket.

H&R Block Inc fell 12.9 percent to $17.19 premarket after the largest U.S. tax preparer said it would miss its fiscal 2010 outlook as high unemployment has led to a drop in tax filings.

(Reporting by Edward Krudy; editing by Jeffrey Benkoe)