SAN FRANCISCO (Reuters) - The old geek's joke about the microchip so warm it can iron your pants or fry an egg could soon be an understatement, according to Intel, the world's largest chip maker. If unchecked, the increasing power requirements of computer chips could boost heat generation to absurdly high levels, said Patrick Gelsinger, Intel Corp. chief technology officer and the chip maker's research visionary. By mid-decade, that Pentium PC may need the power of a nuclear reactor. By the end of the decade, you might as well be feeling a rocket nozzle than touching a chip. And...