[iMore.com]

You may not realize it, but the new Apple A8 processor on the latest iPhone 6 and iPhone 6 Plus can handle 4K video playback even though the smaller Apple phone has a native resolution of 1334 X 750 pixels while the larger Plus model has a 1080p Full HD display with 1920 X 1080 pixels. Though you won't get a pixel-for-pixel output on the phones' screens, the A8's ability to handle 4K playback means that users who sideload 4K content would be able to still watch it on their phones.

Full story from the iMore Blog...