"Their guidance being overly conservative for next quarter, that's what's causing the most chaos in the shares today," said Jim Grossman, portfolio manager at the Thrivent Technology Fund. "People want a little more explanation of why they're giving such conservative guidance." Apple's success, focused much on the iPod and iTunes Music Store, may have distracted investors from its core business: the Mac, which is in the middle of a large-scale shift to new Intel processors and faces challenges. "Historically the Mac has been the primary revenue generator," said Nittin Gupta, an analyst with the Yankee Group. "At this rate of growth, the Mac is not going to be their primary revenue driver. If they become too dependent on iPods and digital audio players, that's a risk over the long term. It's going to be hard to maintain those iPod shipment numbers." Apple shares fell $2.22, or 2.6 percent, to close at $82.49, following disappointing results by Intel (and Yahoo!) on Tuesday. In after-hours trading, Apple stock fell below $78 before rebounding to $79.71, a drop of 3 percent since its close for the day.