The Apple A4 is a 32-bit package on package (PoP) system on a chip (SoC) designed by Apple Inc. and manufactured by Samsung. It was the first SoC Apple designed in-house. The first product to feature the A4 was the first-generation iPad, followed by the iPhone 4, the fourth-generation iPod Touch, and the second-generation Apple TV.[ The A4 uses the PoP method of installation to support RAM. The top package of the A4 used inside the first-generation iPad, the fourth-generation iPod Touch, and the second-generation Apple TV contains two 128 MB LPDDR chips, providing a total of 256 MB of RAM. The top package of the A4 used inside the iPhone 4 contains two 256 MB LPDDR chips, providing a total of 512 MB of RAM. The RAM is connected to the A4 using ARM's 64 bits wide AMBA 3 AXI bus.[
