There are stocks that abide by the principles of logic, and then there's Micron ( MU). Micron, which sells memory to the largely inert PC market, lately has been forced to sell its chips for less than the cost of production. When it reports later this month, it's expected to offer up its 10th-consecutive quarterly loss. Yet its share price has nearly doubled from its year-to-date February low of $6.76, closing Tuesday at $13.15. That's because Micron is trading not on its fundamentals, but according to the volatile ups and downs of DRAM (dynamic random access memory) pricing. All this from a stock that's become an almost legendary punching bag for tech-watchers. "Micron is nothing but an airline with a fab attached, someone once told me," recalls one hedge fund analyst. "They're actually destroying value over time." According to Sanford Bernstein, since 1996, Micron's cumulative free cash flow is about negative $1 billion. More proof of its contrary tendencies: Yesterday, shares vaulted nearly 7% after the company said PC demand was looking better than expected, though the trend may actually hurt rather than help. So how to explain the sudden surge in Micron's stock price? "Money managers know if you're looking for cyclical recovery, buy a really high beta stock. Historically that's been a stock like Micron," explains Sanford Bernstein's Adam Parker, whose firm does not do investment banking. "Nobody really cares about the fundamentals." In practice, that means the chipmaker trades by its own odd rules of sentiment, rising and falling by the vagaries of the DRAM market even as it consistently pumps out abysmal financial results. "When you think of the stabilization in the pricing of DRAM, the best way to play it is Micron," shrugs a money manager who bought into the stock last spring. His exit strategy hinges on DRAM prices, not the promise of fundamental improvements. The short version: Dump the stock when DRAM prices fall steadily for more than a week or so.