In Q1 2007, only 16% of performance desktop PCs were based on quad-core microprocessors. By Q4 2007, that number is expected to rise to 33% and then to 94% by Q4 2009. Quad-core penetration in mainstream desktop PCs will rise to 5% in Q3 2007 and then to 7% by Q4. Penetration will continue to increase in the following months, hitting 18% in the Q4 2008, and then reaching nearly half of the market, at 49%, in Q4 2009, iSuppli says.