Apple is finding that breaking up with Samsung is hard to do.

For evidence, look no further than Apple Inc.'s effort to find a company other than ferocious rival Samsung Electronics Co. to make the sophisticated chip brains used in Apple's iPads and iPhones. This month, after years of technical delays, Apple finally signed a deal with Taiwan Semiconductor Manufacturing Co. to make some of the chips starting in 2014, according to a TSMC executive. The process had been beset by glitches preventing the chips from meeting Apple's speed and power standards, TSMC officials said.

Despite the deal, Samsung will remain the primary supplier through next year, one of these executives said.

Apple is one of Samsung's biggest customers for processors and memory chips. But the two firms compete directly in the mobile-phone market and have spent the better part of the past two years suing and countersuing over the look, feel and features of their gadgets. Both companies declined to comment.