Virata Corp., which supplies semiconductors and software to makers of digital subscriber line equipment, plans to raise as much as $50 million through an initial stock sale, according to its filing with the Securities and Exchange Commission. Backers of the Santa Clara-based company include Oracle Corp., which holds a 13.4% stake. The number of shares to be sold and their estimated price range will be disclosed in a subsequent filing. Virata was incorporated in 1993 after being part of Olivetti Research Laboratory, now AT&T Corp. Laboratories. The company specializes in semiconductors and software for broadband uses. Its components are used in modems, gateways, routers and other types of digital subscriber line, or DSL, equipment. Virata said it would use proceeds from the stock sale for working capital and general corporate purposes. Those purposes may include research development and sales and marketing.