The Apple A7

As we can see, Apple products including iPhone, iPad, iPod Touch, etc are flourishing on current electronic goods market. With the continual update of iPhone products, the 64-bit A7 mobile processor is of great expectation among iPhone users. Is the Apple A7 really that powerful? Well then, certain information about the Apple A7 will be introduced below:

iPhone 5S, which is the only phone on the market with the all-new A7 mobile processor is released by Apple Inc. on September 10, 2013. The Apple A7 is a 64-bit, 1.3GHz, ARMv8, dual-core CPU chip, which makes it twice as fast as the A6 which is universally employed in iPhone 5 and iPhone 5c, as Apple Inc. states. The Apple A7 is only available on iOS 7, which is the operating system that ships on the iPhone 5S. Apple also claims that the chip owns twice the graphics power as its last generation, when it is needed to run high-end games and other apps which have a high demand for high-quality visual effects.

Compared with the ARMv7 adopted in the Apple A6, the ARMv8 instruction set doubles the number of registers of the A7. 31 general purpose registers which are each 64-bit and 32 floating-point /NEON registers which are each 128-bit wide are included in the Apple A7. Owning excellent performance, the Apple A7 integrates a graphics processing unit-GPU in a four cluster configuration. Also, a feature – image processor introduced in the Apple A5 is used in the Apple A7 to facilitate image stabilization, color correction and light balance.

As Apple states, the Apple A7 can be compatible with all 32-bit applications on iOS. Though the Apple Inc. has not claimed the exact RAM of iPhone 5S, it can not be 4GB because of the chip architecture design.
  
Compared with 32-bit A6, the whole performance of A7 is promoted. Moreover, the Apple A7 has twice the integer registers and floating-point registers as its last generation. To load more data, the chip should reduce consistent caching or memory access. By making use of 64-bit integer computing and NEON design, the advantages of the new chip can be exploited to the largest extent.

Drawbacks:
However, there is a severe drawback of the Apple A7: to save a data with same size, the Apple A7 asks for more space than A6. To be specific, a long integer occupies 4 bytes on A6-based iPhone, while 8 bytes is needed to accommodate the same integer. Since more bytes are needed to save the same data, the cache space will be reduced and performance of the device will be affected correspondingly.
  
Another thing which catches many iPhone 5S users’ attention is the effect brought by running third-party apps. Since the vast majority of apps in App Store are 32-bit, iPhone 5S users have to reload corresponding 32-bit edition of certain application after loading 64-bit edition, which inevitably asks for more space for storing operating system files. Therefore, some backend applications must be switched from RAM to floppy memory, and then the operating speed will be influenced.

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