Rambus (Nasdaq: RMBS) is kind of like the hyperactive stepbrother ARM Holdings (Nasdaq: ARMH) never wanted.

While ARM makes its daily bread by developing and then licensing out microprocessor technologies that power the majority of today's smartphones (among other gadgets), Rambus does the same for memory standards. Both companies focus on making chips run faster and cooler on less electrical power, and they have provided investors with periods of volatile returns. The difference is that Rambus runs on lumpy fuel and lots of courtroom controversy, while ARM navigates a steadier course in calmer waters.

For example, Rambus just reported second-quarter sales of $38.9 million -- down 76% from the previous quarter where Samsung signed a pretty big, front-loaded license deal. The very same contract also ensured that the first half of 2010 saw 270% higher total sales than the equivalent year-ago period. The bottom line is just as jumpy: A net loss of $0.11 per share this quarter compares badly to the previous quarter's $1.28 net income per share but looks delightful next to the $0.23 loss per share seen last year.

You just never know where you have Rambus. By contrast, ARM has delivered near-breakeven net results on relatively stable sales since time immemorial in smartphone terms.

That contrast is likely to continue for a while, even if Rambus is working on getting out of this bumpy ride. A 10-year LED lighting license to General Electric (NYSE: GE) is a nice start, but nothing will truly be settled or sane until at least the biggest ones of several long-running legal battles draw to a close. Micron (NYSE: MU) and other memory-chip makers are still fighting Rambus claims for patent licenses and infringement damages, while graphics expert NVIDIA (Nasdaq: NVDA) is defending against similar claims Rambus makes on NVIDIA-designed memory controllers.

There may be enormous windfalls in Rambus' future if either or both of these cases work out in its favor when the legal process shakes down, but in the meantime there's nothing but uncertainty. IBM (NYSE: IBM) and many other technology giants pay Rambus license fees today, generally on five-year terms, but could poor court rulings make IBM or other companies reconsider their future terms or legal options? Perhaps not, but this is the kind of uncertainty that can kill a stock.

So if you're dead set on investing in Rambus, I hope you brought a safety harness and an airsick bag. There's turbulence ahead, in keeping with a decade of jumpy tradition. Sensitive stomachs with an appetite for technology licensing businesses might want to look at ARM instead.

That's my two cents. What's yours? The comments box below is dying to know.