Amazon wasn't the only technology stock to outshine the broader market for tech shares during the last three months. Investors also hit the'play' button on shares of companies that get all or most of their revenue from the computer-games business. Sony (SNE), Activision Blizzard (ATVI), Electronic Arts (EA) and NetEase all posted market-trouncing returns for the second quarter, a period when the Nasdaq was essentially flat. So did shares of Nvidia (NVDA), whose graphics chips are used in powerful computers favored by gamers. The question now for momentum investors is how far the stocks can run, as these issues tend to be volatile.