Photos of what appear to be the logic board of the iPhone 5S have been posted on Japanese site Moumantai. The logic board shown in the images is nearly identical to the one found in the iPhone 5 except for a few minor changes.
The part on the left belongs to the iPhone 5S while the one on the right is the iPhone 5’s logic board. The iPhone 5S component shows us a placeholder for the next generation A series chip, and seems bigger than the corresponding area in the iPhone 5’s logic board.
Apart from that, the shape of the board at the bottom is different, possibly hinting at a different internal arrangement around the speaker area.
The increasing frequency of iPhone 5S related component leaks makes the rumored September-October a likely release timeframe. Like previous “S” upgrades, the iPhone 5S is widely expected to look like the iPhone 5, but come with improved internals such as a faster A-series processor, improved camera system and possibly new features such as fingerprint sensor and NFC.