Genesis Microchip ( GNSS) reaffirmed its fourth-quarter revenue guidance, adding that it expected a slight rise in first-quarter revenue. The company's stock was nevertheless under pressure in the premarket session because of analyst downgrades. Genesis expects sales in the fourth quarter of $55 million, ahead of the average analyst estimate of $50.7 million, according to Thomson Financial/First Call. For the full year, the company expects sales of $160 million, also above the $158 million Thomson Financial/First Call estimate. In the first quarter of 2003, Genesis forecast sales of $60 million vs. an analyst estimate of $52.5 million. The stock was falling 8.4% to $32.60 in Instinet premarket trading after closing at $41 Wednesday on the Nasdaq. Prudential and CIBC both downgraded the stock, with Prudential citing concerns about revenue guidance and the company's tax rate.