The Apple A4 is a 32-bit package on package (PoP) system on a chip (SoC) designed by Apple Inc., part of the Apple silicon series, and manufactured by Samsung. The A4 was the first SoC Apple designed in-house, as the processors for the first 3 iPhone models were designed by Samsung instead. The first product to feature the A4 was the first-generation iPad, followed by the iPhone 4, fourth-generation iPod Touch, and second-generation Apple TV.