NEW YORK ( TheStreet) - GigaMedia ( GIGM) is soaring after it announced that it is selling its majority stake in its online-gaming software business. GigaMedia, an online gaming and software company based in China, is selling 60% of its stake, including its Everest Poker platform, to Mangas Games for $100 million, as well as a later payment based on the unit's fair value in 2012. Giga will retain a 40% stake in the business and has the option to sell all or part of its stake to Mangas starting in 2013. Mangas will be able to buy any remaining shares GigaMedia owns beginning in 2015. Giga expects a "substantial gain" from the sale, which is expected to close in the first quarter of 2010. Shares of Giga Media are spiking 7.9% to $4.09 in morning trading. -- Reported by Jeanine Poggi in New York. >>See our new stock quote page. Follow TheStreet.com on Twitter and become a fan on Facebook.