This article will discuss the processor architecture of ARM Cortex A7 . Semiconductor products based on it can be found in smartphones, routers, tablet PCs and other mobile devices, where until recently it has occupied leading positions in this market segment. Now it is gradually being replaced by newer and fresher processor solutions.
ARM Company Brief
The history of ARM began in 1990, when it was founded by Robin Saxby. The basis for its creation was the new microprocessor architecture. If before this, x86 or CISC occupied the dominant position in the CPU market, then after the formation of this company, a worthy alternative appeared in the form of RISC. In the first case, the execution of the program code was reduced to 4 stages:
Getting machine instructions.
Performing microcode conversion.
Getting micro-instructions.
Phased implementation of micro-instructions.
The main idea of the RIS C architecture was that the processing of program code can be reduced to 2 stages:
Getting RISC instructions.
Processing RISC instructions.
For example, in the first and in the second case there are both pluses and significant disadvantages. x86 successfully conquered the computer market, and RISC ( including the ARM Cortex A7 , introduced in 2011) - the market for mobile devices.
The story of the appearance of the Cortex A7 architecture. Key Features
The basis for the “Cortex A7” was the “Cortex A8”. The main idea of the developers in this case was to increase productivity and significantly improve the energy efficiency of the processor solution. This is exactly what ultimately happened with the engineers at ARM . Another important feature in this case was that it became possible to create CPUs with big.LITTLE technology . That is, a semiconductor chip could include 2 computing modules. One of them was aimed at solving the simplest tasks with minimal power consumption and, as a rule, the Cortex A7 cores played in this role. The second was designed to run the most complex software and was based on the Cortex A15 or Cortex A17 computing units. Officially, the “Cortex A7” was introduced, as noted earlier, in 2011. Well, the first ARM Cortex A7 processor was released a year later, that is, in 2012.
Production technology
Initially, A7-based semiconductor products were manufactured according to 65 nm technological standards. This technology is now hopelessly outdated. In the future, two more generations of A7 processors were released according to the tolerance standards of already 40 nm and 32 nm. But even now they have become irrelevant. The latest CPU models based on this architecture are already manufactured at 28 nm standards, and it is precisely them that can still be found on sale. It is hardly worth expecting a further transition to newer technological processes with new tolerance standards and outdated architecture. A7-based chips now occupy the most low-cost segment of the mobile device market and are gradually being replaced by gadgets based on the A53, which with practically the same energy efficiency parameters have a higher level of performance.
Microprocessor core architecture
1, 2, 4 or 8 cores can be part of a CPU based on ARM Cortex A7. The characteristics of the processors in the latter case indicate that the chip includes essentially 2 clusters of 4 cores. For 2-3 years, entry-level processor products were based on chips with 1 or 2 computing modules. The average level was occupied by 4-core solutions. Well, the premium segment was behind the 8-core chips. Each microprocessor core based on this architecture included the following modules:
There were also the following common components for all cores in the CPU:
Possible frequencies
The maximum clock frequency for this microprocessor architecture can vary from 600 MHz to 3 GHz. It should also be noted that this parameter, which indicates the maximum effect on the performance of the computing system, is changing. Moreover, three factors immediately affect the frequency:
The level of difficulty of the problem.
The degree of software optimization for multithreading.
The current temperature of the semiconductor crystal.
As an example, consider the MT6582 chip operation algorithm, which is based on A7 and includes 4 computing units, the frequency of which varies from 600 MHz to 1.3 GHz. In idle mode, this processor device can have only one unit of calculations, and it operates at the lowest possible frequency of 600 MHz. A similar situation will be in the case when a simple application is launched on a mobile gadget. But when a resource-intensive toy with optimization for multithreading appears in the task list, then all 4 blocks of processing the program code at a frequency of 1.3 GHz will automatically turn on. As the CPU heats up, the hottest cores will lower the frequency or even turn off. On the one hand, this approach provides energy efficiency, and on the other, an acceptable level of chip performance.
Cache memory
Only 2 cache levels are provided in the ARM Cortex A7. The characteristics of the semiconductor crystal, in turn, indicate that the first level is necessarily divided into 2 equal halves. One of them should store data, and the other - instructions. The total cache size at the 1st level by specifications may be equal to 64 Kb. As a result, we get 32 Kb for data and 32 Kb for code. L2 cache in this case will depend on the specific CPU model. The smallest volume of it can be equal to 0 Mb (that is, absent), and the largest - 4 Mb.
RAM controller. Its features
Any ARM Cortex A7 processor is equipped with an integrated RAM controller. Specifications technical plan indicate that it is focused on work in conjunction with RAM standard LPDDR3. The recommended operating memory frequencies in this case are 1066 MHz or 1333 MHz. The maximum RAM size that can be found in practice for this chip model is 2 GB.
Integrated graphics
As expected, these microprocessor devices have an integrated graphics subsystem. ARM manufacturing company recommends using a proprietary Mali graphics card - 400MP2 in combination with this CPU. But its performance is often not enough to unleash the potential of a microprocessor device. Therefore, chip developers use more powerful adapters, for example, Power VR6200 , in combination with this chip .
Software Features
Three types of operating systems target ARM processors:
All the rest of the system software has not yet been widely distributed. It is not difficult to guess that the largest market share of such software is Android. This system has a simple and intuitive interface and entry-level devices based on it are very, very affordable. Until version 4.4 inclusive, it was 32-bit, and with 5.0 it began to support 64-bit computing. This OS successfully runs on any RISC CPU family, including the ARM Cortex A7. The engineering menu is another important feature of this system software. With its help, you can significantly reconfigure the capabilities of the OS. Access to this menu can be obtained using the code, which is individual for each CPU model.
It is also an important feature of this OS - the installation of all possible updates automatically. Therefore, even new features may appear on the ARM Cortex A7 family of chips. Firmware can add them. The second system targets APPLE's mobile gadgets . Such devices mainly occupy the premium segment and have appropriate levels of performance and cost. The latest OS in the face of Windows Mobile has not yet received wide distribution. There are devices based on it in any segment of mobile gadgets, but a small amount of application software in this case is a limiting factor for its distribution.
Processor models
The most affordable and least productive in this case are 1-core chips. The most widespread among them was MT6571 from MediaTech. A notch is the ARM Cortex A7 Dual Core dual-core CPUs. An example is MT6572 from the same manufacturer. An even higher level of performance was provided by the Quad Core ARM Cortex A7. The most popular chip from this family is the MT6582, which now can even be found in entry-level mobile gadgets. Well, the highest level of performance was provided by the 8-core central processors, to which the MT 6595 belonged .
Further development prospects
You can still find mobile devices on the shelves of stores based on a 4X ARM Cortex A7 based semiconductor processor device. These are the MT6580, MT6582 and the Snapdragon 200. All these chips include 4 computing units and have an excellent level of energy efficiency. Also, the cost in this case is very, very modest. But still the best of times are microprocessor architecture is already behind. The peak of sales of products based on it fell in 2013-2014, when it had practically no alternative to the mobile gadget market. And in this case we are talking about both budget devices with 1 or 2 computing modules, as well as flagship gadgets with an 8-core CPU. At the moment, it is gradually being replaced by the Cortex A53, which is essentially a modified 64-bit version of A7. At the same time, she retained the main advantages of her predecessor entirely and completely, and the future is certainly hers.
The opinion of experts and users. Real reviews of chips based on this architecture. Advantages and disadvantages
Of course, a landmark event for the world of mobile devices was the emergence of the architecture of microprocessor devices ARM Cortex A7. The best proof of this was that devices based on it have already been successfully sold for more than 5 years. Of course, now the capabilities of A7-based CPUs are no longer enough even to solve mid-level tasks, but the simplest program code on such chips continues to function successfully to this day. The list of such software includes video playback, listening to audio recordings, reading books, web surfing and even the most simple toys in this case will start without any problems. It is on this that the attention is focused on the leading thematic portals devoted to mobile gadgets and devices, both leading specialists of this plan and ordinary users. The key minus of the A7 is the lack of support for 64-bit computing. Well, the main combination of it can be attributed to the perfect combination of energy efficiency and productivity.
Summary
Of course, the ARM Cortex A7 architecture is an era in the world of mobile devices. It was with its advent that mobile devices became affordable and quite productive. And the mere fact that it has been successfully sold for more than 5 years is another confirmation of this. But if at first gadgets based on it occupied the middle and premium segments of the market, now only the budget class is left behind. This architecture is outdated and is gradually becoming a thing of the past.