NEW YORK (TheStreet) -- There were more records to be broken by the S&P 500 and Dow Jones Industrial Average on Monday, even if the day's gains were only modest. 

Apple (AAPL) helped to boost markets after another vote of confidence from activist investor Carl Icahn, while semiconductor stocks rallied on reports Intel (INTC) and Altera (ALTR) had reopened negotiations.

The S&P 500 gained 0.3% to a record 2,129, extending gains achieved last week. The Dow rose 0.14% to a high of 18,297. The Nasdaq climbed 0.6%.

Apple shares rose 1.2% on Monday to $130.35 after activist investor Carl Icahn called current valuation "undervalued." He said Apple is worth $240 a share. In a letter to Apple CEO Tim Cook, Icahn also called for accelerated buybacks. Click here for more.

"After reflecting upon Apple's tremendous success, we now believe Apple shares are worth $240 today," wrote Icahn. "Apple is poised to enter and in our view dominate two new categories (the television next year and the automobile by 2020) with a combined addressable market of $2.2 trillion, a view investors don't appear to factor into their valuation at all."

Intel and Altera reportedly have restarted negotiations surrounding a potential deal, according to the New York Post. Altera had previously rejected a $54-a-share deal in April. Altera shares jumped nearly 7%.

Chipmakers Skyworks (SWKS), Qorvo (QRVO), Avago (AVGO), and Himax (HIMX) were all higher. The iShares PHLX Semiconductor ETF (SOXX) added 1%.

Other major tech companies including LinkedIn (LNKD), Facebook (FB), and Cisco (CSCO) were higher, while the Technology SPDR ETF (XLK) added 0.5%.

Endo Pharmaceutical (ENDP) was the worst performer on the S&P 500 after the company agreed to buy privately held Par Pharmaceutical Holdings for $8.05 billion in cash and stock. The deal would create one of the five largest generic drugmakers in the U.S.

Ann (ANN) rocketed nearly 20% higher after being acquired by Ascena Retail Group (ASNA) for $47 a share. The deal values Ann, owner of Loft and Ann Taylor, at around $2 billion.

Splunk (SPLK) fell more than 4% after the company unexpectedly named Snehal Antani as chief technology officer. No update has been given as to the status of former CTO Todd Papaioannou.

Chinese microblogging site Weibo (WB) plummeted 5.5% after Summit Research downgraded the stock to hold. Last week, Weibo provided soft second-quarter guidance that rattled investors.

Alibaba (BABA) was lower after luxury clothes maker Kering filed a suit against the e-commerce giant, alleging it allowed counterfeit versions of its brand on the site.

BHP Billiton (BHP) plunged 6.2% after the company's South32 spinoff was valued at around $9.1 billion, the lower end of expectations. The split will allow BHP to focus on its businesses in iron ore, petroleum and coal.

A measure of homebuilder confidence declined 2 points to 54 in May, though remained above the 50 level indicating optimism, according to the National Association of Home Builders/Wells Fargo data. The gauge was pulled lower by signs of weakness in sales of single-family homes. Economists had expected the measure to increase to 58.

"Despite general optimism for most sectors of the economy, [Federal Reserve] officials have been quite critical of the housing market, continuing to characterize the recovery as downright 'slow'," said Lindsey Piegza, chief economist at Sterne Agee. "This morning's drop in the NAHB simply reinforces the Committee's lackluster assessment of the US housing recovery."

The Fed could hike interest rates sooner than expected with Chicago Fed President Charles Evans noting overnight in a speech that a June hike is a possibility. Evans, speaking in Stockholm, also said the Fed wouldn't likely reach its 2% inflation target until 2018. The majority of economists believe the Fed will hike no sooner than September.

Fed Chair Janet "Yellen and [New York Fed president William] Dudley gave words that suggested they fully expect volatility around the hiking idea which is another way of saying the Fed won't be swayed to postpone their intent simply because the markets are jumping about," said CRT Capital Group's Ian Lyngen.

More from Markets

Inside Carnival's Mind Blowing New Horizon Cruise Ship (Video)

Inside Carnival's Mind Blowing New Horizon Cruise Ship (Video)

Jim Cramer: The 10-Year Yield Could Go to 2.75%

Jim Cramer: The 10-Year Yield Could Go to 2.75%

Oil Slumps, Gas Spikes Ahead of Holiday Weekend; Assessing the Chipmakers--ICYMI

Oil Slumps, Gas Spikes Ahead of Holiday Weekend; Assessing the Chipmakers--ICYMI

Week Ahead: Wall Street Looks to Jobs Report as North Korea Meeting Less Certain

Week Ahead: Wall Street Looks to Jobs Report as North Korea Meeting Less Certain

Dow and S&P 500 Decline, Energy Shares Fall as U.S. Crude Oil Slides 4%

Dow and S&P 500 Decline, Energy Shares Fall as U.S. Crude Oil Slides 4%