Volume production of Apple’s next-generation A9 application processor, which is expected to power the company’s upcoming iPhone model, has begun at facilities operated by Samsung and Taiwan Semiconductor Manufacturing Company (TSMC), a report said Thursday. Apple is rumored to be working on at least two iPhones, commonly referred to as the “iPhone 6S” and “iPhone 6S Plus,” for launch this year.

The report by Taiwan’s DigiTimes said that Apple has requested Samsung and TSMC to make last-minute changes to the chip layout, but the modifications are not expected to affect the launch schedule of the new handsets. The report also said that TSMC will only begin mass production of the A9 chips in the fourth quarter of 2015, using its 16-nanometer FinFET process.

However, if Apple sticks to its typical September launch schedule for the new iPhone, TSMC will not be able to make a significant contribution to the initial iPhone 6S units, at least in terms of processors, Apple Insider reported. In addition to producing the A9 chips, TSMC is also reportedly responsible for the production of Touch ID sensors and audio chips for the new iPhone.

Apple-iPhone6 The iPhone 6 is displayed at an Apple Store on Sept. 19, 2014 in Palo Alto, California. Photo: Justin Sullivan/Getty Images

Apple is reportedly preparing for a larger initial production run of the new iPhones, which are expected to come with 4.7-inch and 5.5-inch displays, and has asked suppliers to manufacture between 85 million and 90 million units of both models. In comparison, the company ordered between 70 million and 80 million units of its iPhone 6 and iPhone 6 Plus last year.

Although the upcoming iPhones are likely to be identical to their predecessors in most respects, there are some new features that are expected to count as an upgrade. 

Rumors have it that the iPhone 6S and iPhone 6S Plus could feature an A9 processor with 2GB of RAM, a much faster Qualcomm LTE chip, a 12-megapixel rear-facing camera with Sony’s RGBW technology and the 7000 Series aluminum that was used in the Apple Watch Sport. The new devices are also rumored to sport a pressure-sensitive control system called Force Touch, which was introduced with the Apple Watch.