Apple has finally bought PA Semi, the fab-less low-power PowerPC start-up that supposedly swooned when Apple switched from the PowerPC Intel.

What Apple’s going to do with it now become fodder for the speculators. The iPhone uses an 32-bit ARM-derived chip that Intel would love to displace with its newfangled Atom processor.

Forbes, which lays the acquisition to Apple CEO Steve Jobs, broke the story a day before Apple reported its earnings on Wednesday.

Forbes thinks it’s to differentiate the iPhone and future iPods. And it would be something Apple totally owns, which sounds like Stevie boy, and would certainly limit reverse engineering. It also thinks that it’ll take at least year for Apple to incorporate it.

Apple is reportedly paying $268 million cash.

To recap old stories, PA was started five years ago by Alpha and StrongARM’s daddy Dan Dobberpuhl and 14 months ago announced a 2GHz 64-bit dual-core PowerPC derivative dubbed the PWRficient that was supposed to need three to four times less power than other similarly minded chips – something like 4W-7W – and be very “system-on-a-chip.”

It wasn’t supposed to ship in volume until lately, which may be a key fact, and Intel is now better on energy efficiency – which leaves observers scratching their heads.

A PA quad was supposed to follow this year and to drown its sorrows over the Apple loss PA went into storage.

Meanwhile, Apple’s fiscal Q2 earnings jumped 36% to $1.05 billion, or $1.16 a share, on revenues up 43% to $7.5 billion on the back of solid Mac sales despite the so-called recession.

It did however forecast earnings this quarter below expectations at a buck a share on revenues of $7.2 billion rather than $1.10 on $7.16 billion with a flat gross margin.

Mac shipments were up 51%, three-and-a-half times the market to 2.289 million units, better than the 2.1 million expected. iPod sales were flat year-over-year at 10.6 million units and the company sold 1.7 million iPhones.