(Reuters) – A Chinese state-owned company offered to buy Montage Technology Group, a Shanghai-based chipmaker, in a deal valued at about $600 million, roughly four months after failing to buy rival RDA Microelectronics Inc. Shanghai Pudong Science and Technology Investment Co Ltd offered $21.50 per Montage share in cash, a 25 percent premium to the company’s closing price on Friday. Shares of Montage, which counts Intel Corp among its top shareholders, were up 19.5 percent at $20.51 in early trading on the Nasdaq. The fabless chipmaker, which went public at $10 per share in September, makes analog and mixed-signal chips for set-top boxes and servers for cloud computing, and counts the world’s four largest DRAM chipmakers as its customers. Topeka Capital Markets analyst Suji De Silva said it was difficult to predict if there would be rival offers since Montage was not a cellphone-focused chipmaker, unlike RDA and Spreadtrum Communications Inc. “But the price seems low, so there could be chance of topping up,” De Silva said.