Indiabulls Securities Research has upgraded its rating on Satyam Computer Services to buy in its August 14, 2008 research report. "Satyam Computer Services Ltd (Satyam) reported a top-line growth of 8.5% qoq to Rs 26.2 billion, driven by a strong dollar and a modest growth in the sales volume (up 3% qoq).Our DCF valuation assuming Rf of 9.0%, terminal growth rate of 5% and WACC of 14.7%, gives a fair value of Rs 557, which is 35% more than the current levels. Hence, we upgrade our rating to Buy," says Indiabulls Securities' research report.