Apple opted for an improved dual-core processor, dubbed the A6. The A series chips are designed by Apple and currently manufactured by Samsung. As an application processor, the A6 is twice as fast as the A5 in the iPhone 4S, and offers twice the graphics performance. Apple appears to have achieved this by moving to a smaller silicon process: The actual chip in the phone is 22% smaller. Again, that frees up more internal space, and it improves power efficiency.

Importantly, Apple has improved battery life, despite the more powerful CPU, the larger screen and LTE support. Talk time on 3G is the same for iPhone 5 and 4S at eight hours; standby time for the new phone is 225 hours, versus 200 for 4S. Internet use on iPhone 5 is eight hours on 3G and on LTE, and 10 hours on Wi-Fi. For iPhone 4S: six hours on 3G, nine on Wi-Fi.

Thanks to other changes in the new CPU, photo and image processing is faster. The A6 has a new image signal processor (ISP) built in, with a feature called spatial noise reduction and a special filter that essentially guides the ISP.

The new iPhone retains the 8-megapixel iSight camera and its f/2.4 aperture. But if offers better low-light performance, 40% faster photo capture, more precise lens alignment and a highly durable sapphire lens cover. Overall, the unit is 25% smaller. Apple also improved the camera's image stabilization, to minimize blurring.

The front-facing camera now supports 720p high definition for higher quality Facetime video chats.