Updated from 10:31 a.m. ESTGraphics cards aren't just for PCs anymore. That's the message Nvidia ( NVDA) and ATI Technologies ( ATYT), the leading graphics-chip specialists, have been trying to get through to investors in recent years. With their core PC markets under attack by Intel ( INTC), both companies have started to roll out versions of their chips targeting a variety of non-PC devices, including mobile phones, digital TVs and medical equipment. Those investments have started to pay off, and for both companies, those non-PC products are becoming increasingly important to their top and bottom lines. But some analysts question just how big the market for graphics chips outside the PC industry will become and how well Nvidia and ATI will be able to compete. "They are to be congratulated for diversifying, but ... shareholders should not get overenamored with the diversification efforts as being the path to riches," says Jon Peddie, an analyst from Jon Peddie Research, which focuses on the graphics-chip industry. At first glance, the non-PC markets seem to represent a promising opportunity for the graphics-chip makers. The global handset market is fast approaching a billion units, for instance, and the digital television market is growing to tens of millions of units in the U.S. alone. Even if Nvidia and ATI were to capture only small fractions of those two markets, that could translate into millions of chips. As ATI has expanded from producing graphics chips for PCs to entering the consumer electronics markets, the company believes that the total addressable market for its products has gone from about $5 billion a year to around $13 billion, says Matt Skynner, the company's vice president of corporate marketing. Meanwhile, Nvidia believes it could eventually see a billion dollars in sales just from its business of selling graphics chips for mobile phones, says Mike Hara, Nvidia's vice president of investor relations and communications.