Overview of mobile platforms (March 2013)

This article describes hardware and software division on the mobile platform market. “Mobile platform” means mass handheld devices with an autonomous power source designated for solving a large variety of general tasks: entertainment, communications and business. This article does not examine personal desktop computers and their portable versions (notebooks/netbooks/etc.)

Information in the article was gathered from public sources available as of the beginning of 2013. Information in the article is indicated taking into consideration software developers’ demand for mobile devices.

Processor architectures

ARM

ARM architecture was developed by ARM Holdings on 1983 as the foundation for a simple and effective processor. The set of instructions is based on the 32-bit RISC-architecture and allows one to operate 14 general registers. Also, the THUMB mode is supported which allows one to cut down on the amount of code needed due to a cut back on using part of the registers. It is possible to use additional software enhancements for a floating point and SIMD operations. Currently, all versions of ARM support only a 32-bit set of instructions.
64-bit versions are to be supported in the future. One interesting fact is that ARM Holdings does not make ready-made chips itself, but rather it only designs processor units and licenses them for outside producers. This positively impacts the price and capabilities for integrating the processing unit with other devices. Over the last 10 years the ARM architecture has been dominant on the mobile device market.

• Developer: ARM Holdings

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• Type of instruction set: RISC

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• Instruction size: 4 bytes (2 for the THUMB mode)

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• Word size: 32 bit

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• Features: optional support of FPU and SIMD

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• Memory model: flat

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• Operating frequency: up to 1.4 GHz

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• Supporting multiple cores

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• High energy efficiency

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• Flexible unit licensing policies

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Versions

The ARM architecture is mostly developing in two main areas: enhancing the main architecture and adding additional peripheral units. The architecture is developing pretty slowly and currently is on version 7. The most relevant are versions 6 and 7 since the earlier ones have too low performance for modern-day processing units.
The architecture with a standardized set of peripheral devices is singled out into a family. So, the architecture with version 6 of the SIMD unit and supporting Thumb is the ARM11 family. The architecture of version 7 with SIMD, Thumb units and other added features form the Cortex family.
ARM architectures are backwards compatible meaning that the code written under the architecture’s version 6 will work on the architecture 7.
The code for newer versions will work on the old ones if it doesn’t use any specific features in the new versions which is a rarity for most practical software. Generally, new versions differ from older ones due to various internal optimizations (in addition to new instructions) which do not directly impact the code.

MIPS

MIPS architecture was presented by MIPS Technologies in 1981. MIPS is based on the RISC set of instructions and it allows one to operate a 31 registers. Support of 64-bit instructions has been added in the latest revisions. Also, now there is optional support of FPU and SIMD operations. Like ARM, the architecture is licensed out to chip producers.
Currently MIPS architecture is mostly used in built-in devices. Also, it is used in Sony Playstation 2 and Playstation Portable gaming consoles.

• Developer: MIPS Technologies

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• Type of instruction set: RISC

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• Instruction size: 4 bytes

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• Word size: 32, 64 bit

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• Features: supports FPU and SIMD

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• Memory model: flat

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• Operating frequency:

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• Supporting multiple cores

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Versions

As of 2000 two architecture versions are still relevant: MIPS32 and MIPS64 which are 32 and 64-bit respectively.

X86

X86 architecture has been developed by Intel since 1978. Since its emergence it has developed from a 16-bit processor working at 5 MHz to 64-bit multi-architecture systems with frequencies up to 4 GHz, a multi-megabyte built-in cache and all the cutting edge enhancements for data processing.
The current processors still support the majority of capabilities from the earliest models which are no longer needed which has a relatively negative impact on the overall architecture’s complexity and its energy consumption. The architecture uses the CISC set of instructions which creates additional complications when writing code and developing optimizing compilers for such an architecture.
Processors based on X86 are produced by a relatively limited group of companies (Intel, AMD and VIA). The architecture is not licensed separately, but rather it is only supplied in the form of readymade products. This negatively impacts the price and the simplicity of integrating processing units in other systems.
The X86 architecture dominates on the PC market.
X86 hasn’t been able to be particular successful in the mobile device niche due to its high energy consumption and low accessibility. The low-performance 32-bit Intel Atom processors are currently used in serial devices.

• Developer: Intel

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• Type of instruction set: CISC

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• Instruction size: 1-15 bytes

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• Word size: 16, 32, 64

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• Features: Supports FPU and SIMD, hyperthreading

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• Memory model: segment (obsolete), flat

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• Operating frequency: up to 4GHz

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• Supporting multiple cores

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• Low energy efficiency

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• Ready-made chips are made by a limited number of producers

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Versions

X86 processors have developed by gradually increasing their speed and expanding the set of instructions. This is no difference between processors from the same generation except for the amount of built-in cache memory and clock speed. 32-bit Atom processors are used in mobile devices as part of the Intel Medfield platform.