Sources in Taiwan claim that Apple is working on a new version of the A4 processor for the iPhone 5.
According to a report on the Apple Daily website (translation here) Apple has been in contact with component manufacturers about creating a new A4 chip designed to power the next generation of the iPhone and the iPad.
Based on ARM's architecture and manufactured by Samsung, the A4 uses the System-on-Chip (SoC) - where all components are integrated into a single circuit - principle. With a clockspeed of 1GHz it is thought that it would lack the power required for the second-generation iPad if rumours of a resolution boost are correct.
The report suggests the new processor could have a dual-PowerVR SGX 543 graphics and video core, as opposed to its predecessor's PowerVR SGX 535 GPU. This will boost performance for higher-resolution graphics and video, potentially even bringing support for 1080p HD content.
It also suggests that the new processor will be called the A8, though this could be the result of some confusion - the current Apple A4 chip uses ARM's Cortex-A8 processing core. None of the details have been confirmed by Apple or any of the component manufacturers in question.