Apple today dramatically increased its stake in PowerVR graphics designer Imagination Technologies through a purchase of a total of 13.72 million extra shares. The move, which includes both 2.2 million extra shares as well as 11.52 million shares on the existing market, well over doubles the original 3.6 percent stake bought late last year to 9.5 percent. It's believed the extra investment is a reaction to Intel, which last week increased its own stake a second time to 14 percent.

The investment is considered important for Apple, which uses only PowerVR graphics in its iPhone and iPod touch devices. Its most recent launch, the iPhone 3GS, uses a PowerVR SGX video core now believed to be the SGX535. Imagination's technology allows for programmable shaders (visual instructions) that roughly match the visual features available to desktop and notebook graphics chips but in a small and power-efficient enough form to fit in a smartphone.

Intel uses PowerVR technology in newer versions of its ultra-mobile Atom platform and will make it key to its Pine Trail platform late this year.