Apple A4
system on a chip (SoC) designed by Apple Inc.
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.
The last operating system update Apple provided for a mobile device containing an A4 (that being the iPhone 4) was iOS 7.1.2, which was released on June 30, 2014 as it was discontinued with the release of iOS 8 in September 2014. The iPad (1st generation) and fourth generation iPod Touch were discontinued earlier than the iPhone 4, with the former last receiving iOS 5.1.1 on May 7, 2012, mainly due to some of iOS 6 new features required a rear & front camera (as the iPhone 3GS, which had a rear camera and weaker hardware, received iOS 6 update with limited new features), while the latter last receiving iOS 6.1.6 on February 21, 2014, as iOS 7 drops support for devices with less than 512MB of RAM. The last operating system update Apple provided for an Apple TV containing an A4 (that being the second-generation Apple TV) was Apple TV Software 6.2.1, which was released on September 17, 2014.
Design
Apple engineers designed the A4 chip with an emphasis on being "extremely powerful yet extremely power efficient." The A4 features a single-core ARM Cortex-A8 central processing unit (CPU) manufactured on Samsung's 45 nm fabrication process using performance enhancements developed by chip designer Intrinsity (which was subsequently acquired by Apple) in collaboration with Samsung. The resulting CPU, dubbed "Hummingbird", is able to run at a far higher clock rate than previous Cortex-A8 CPUs while remaining fully compatible with the Cortex-A8 design provided by ARM. The same Cortex-A8 used in the A4 is also used in Samsung's S5PC110A01 SoC. The A4 also features a single-core PowerVR SGX535 graphics processing unit (GPU). The die of the A4 takes up 53.3 mm2 of area.
The clock rate of the Cortex-A8 in the A4 used inside the first-generation iPad is 1 GHz. The clock rate of the Cortex-A8 in the A4 used inside the iPhone 4 and fourth-generation iPod Touch is 800 MHz (underclocked from 1 GHz). It is unknown what the clock rate of the Cortex-A8 in the A4 used inside the second-generation Apple TV is.
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