The MCX Stock Exchange (MCX-SX) benchmark index SX40 went live with its equity trading platform on both equities and equity derivatives today. MCX-SX became the third full-fledged equity bourse after BSE and NSE in the country. The bourse was formally launched by Finance Minister P Chidambaram on Saturday.SX40 is a free-float based index of large-cap and liquid stocks, representing diverse sectors. The base value will be 10,000 with a base date of March 31st, 2010.In the early trade,Reliance Industries, Suzlon and NHPC were leading the volume chart, while the value chart was being led by RIL, SBI, Tata Steel and Reliance Capital.The benchmark includes companies that have a minimum free float of 10 per cent and is within the top 100 liquid companies.