Arm and x86 comparison

Believe it or not, just grab a man and ask him if he knows the CPU, I think his answer will be sure, but if you ask him again do you know the structure of arm and X86? What is the difference between the two? The vast majority of people must be a face. Today's small make up to take you in-depth understanding of the CPU of these two major architectures: arm and X86. Go out and put X on it!
# # Relive what the hell is the CPU #
Central processing Unit (CPU) mainly by the operator, controller, register three parts, from the literal meaning of the operator is to play the role of operation, the Controller is responsible for the issue of CPU each instruction required information, register is to save the operation or instructions of some temporary files, so as to ensure a higher speed
CPU has the processing instruction, carries on the operation, the control time, the processing data four big functions, metaphorically speaking, the CPU is like our brain, helps us to complete each kind of physiological activity. Therefore, if there is no CPU, then the computer is a pile of waste, can not work. Mobile devices are actually very complex, and these CPUs need to execute millions of instructions to make it work in the direction we expect, and CPU speed and power efficiency are critical. Speed affects the user experience, and efficiency affects battery life. The most perfect mobile device is the combination of high performance and low power.

To understand X86 and arm, you have to understand the complex instruction set (CISC) and reduced instruction set (RISC) from the CPU to the present, there are very many architectures, from our familiar X86, ARM, to the unfamiliar MIPS, IA64, the gap between them is very large. But if sorted from the most basic logical point of view, they can be divided into two categories, the so-called "complex instruction set" and "reduced instruction set" system, which is often seen as "CISC" and "RISC".

The first difference between Intel and ARM processors is that the former uses a complex instruction set (CISC) and the latter uses a compact instruction set (RISC). The biggest difference between the various architectures that fall into the two categories is that their designers consider the different ways in which they are concerned. The following small series are introduced separately:

X86:intel a single big

When it comes to chip giants Intel, every Internet user should not be unfamiliar, Intel's CPU manufacturing technology is global, but do you know how the giant company made its fortune?

As of June 8, 1978, Intel has released a new microprocessor, "8086". The processor didn't get much attention when it came out, but he created a new era. 8086 means the birth of the x86 architecture, while x86 as a specific microprocessor to execute the instruction set of the computer language, defines the basic use rules of the chip. 8086 also directly led Intel to become the world's leading chip giants.
and x86 not only made Intel a meteoric rise, but also became a standard in the industry. In the past few decades, whether it is notebook, server, supercomputer or writing equipment, can see x86 figure. Furthermore, the x86 architecture is being improved through a variety of methods, both AMD and Via, which can X86 the flexibility of the instruction set against Intel, forcing x86 to change.

Through decades of technology accumulation, x86 server in the field of server status is almost alone and defeated. The small and flexible x86 server is widely used in the market, and it can be used in many fields such as file, print, communication, web, email, database and application services in the Internet and LAN.

The biggest feature of the x86 server is that it can be compatible with Windows operating systems, all with Intel's CPU. and Intel's x86 server can be divided into two generations, the original 80x86 series after the release of product 80486, Intel has renamed and registered the series, which is now Intel's Pentium series, of course, this series in China also has a more resounding name, That is, the Pentium series.

Current Pentium series CPUs include: Pentium, Pentium MMX, Pentium Pro, PII, Pii Xeon (Xeon), PIII, PIII Xeon, P4 Xeon, Celeron2 (Celeron), and so on.

X86:40 for many years to insist

x86 old? From the time, it's really old. x86 has been nearly 40 years since 1978. After a variety of vicissitudes, x86 is still the absolute leader of the server industry, saying that such a server industry leader has been old, it is only in the accusation to support the entire Internet server industry has been old.

And, after many generations of improvements and transformations, the x86 architecture server is still one of the fastest architectures. And now x86 is also the industry's benchmark, from the technical point of view x86 has never lagged behind, but with other architectures compared to the size of the server is not narrowed.

Judging from the instruction set architecture, CISC is really a bit stale. Even Intel has acknowledged that the CISC architecture does limit the development of CPUs. In the CISC microprocessor program of each of the instructions in tandem execution, the instruction operation also needs serial execution, in accordance with this way to carry out the task, the control of course is very simple, but the overall utilization of the computer is dragged back, the implementation speed is relatively slow. This is one of the reasons why the CISC architecture is used for middle and low servers.

Complex instruction set is a kind of instruction set which exists with the birth of computer. It has a strong ability to deal with high-level languages, to improve the performance of the computer has some benefits. The increasingly complex instruction system not only brings the inefficiency, but also causes the complexity of the system structure to increase, this complexity will also lead to the cisc of the general poor.

ARM: Mobile end of the sudden rise

In the PC World, Intel's CPU is a solo show. And on the mobile side? Then it's arm. ARM is all called Advanced RISC Machine, that is, advanced streamlined instruction set machine. Arm is one of the representative works of RISC microprocessor, which is widely used in the design of embedded system. And the biggest feature of ARM processor is energy-saving, which is one of the reasons for its no enemy in the field of mobile communications.

Create a ARM64 bit server
In the past, arm focused on the development of 32-bit architecture, the mobile end of the hegemony for many years, so that the Intel envious. And in the PC and server domain, Intel's market also makes arm very jealous. The first 64-bit processor was released by arm at the end of 2011, and Dell released its first ARM64 server based on the ARMV8 in 2013, and the corresponding server solution was developed.
Experts believe that although Intel's x86 processor is still invincible in the server sector, but the 64-bit ARM architecture should be able to find its own place, arm in the memory and network interface with the calculation of the core of the distance will be as close as possible, and to carry the high density of a large number of computing processes, This feature fits well with Web servers and their applications.

In the server domain, Intel's chips also have many areas of acclimatized, such as memory capacity, I/O and processing performance is disproportionate, the performance of the ARM processor will be more qualified. The complexity of the ARM processor Isa much lower, the development cost is also low, correspondingly, the server developed by the ARM server manufacturer for these scenarios has the precondition of defeating Intel. And from these application environment into the server market ARM architecture Server for customers is also the original part of x86 customers.

And Intel is not easy to let go, in the server area, its process for arm to stay ahead, its processor performance is much higher than the ARM processor, can be in power consumption has been a heart of Intel.

In addition, Intel also wants to enter the mobile end, to beat Arm, in the Low-power server field is a good choice. Using the 14nm process of xeon-d, which includes 2 1.4G Broadwell kernel and GPU power consumption only 6W, in the performance of power consumption than arm is much higher than a lot.

In 2008, Intel launched the Atom processor, the smallest and least-consumed processor in Intel's history, that was created to make up for its own weaknesses in mobile computing, a field that has been occupied by arm for many years and which Intel has no advantage in technology and experience. It's not easy to beat arm?

Since both sides are eyeing each other's fields, the battle between arm and Intel is absolutely inevitable. So want to enter the Intel server domain, arm need to come up with the real ability, with its 64-bit processor as the basis of the chip design, low power consumption, low cost, have the flexibility of architecture, with these advantages to hard touch Intel can have a few chances?

In other words, the ARM chip architecture has the flexibility to achieve many of the characteristics of the enterprise requirements, such as cache consistency and fault tolerance and high availability, the software's environmental maturity is less than Intel, even with more corporate attention may not be able to be confident to defeat Intel, So what is supporting this arm to challenge intel away?

Arm and X86

Comparing arm and X86 architectures Intel and ARM processors from several aspects, in addition to the most essential complex instruction set (CISC) and reduced instruction set (RISC) difference, below we can compare the arm and the X86 architecture from the following several aspects.
1, manufacturing process The big difference between arm and Intel processors is that ARM has never designed a low-power processor, and Intel's strength is in designing ultra-high performance desktops and server processors.

Intel has long been the boss of the desktop server industry. However, when entering the mobile industry, Intel still uses the same complex instruction set architecture as the desktop, trying to cram it into smaller processors that are used by mobile devices. But the Intel i7 processor has an average heating rate of 45 watts. The maximum instantaneous peak calorific value of the on-chip system based on ARM is about 3 watts, about 1/15 of the Intel i7 processor. Its newest Atom-series processor uses a temperature-control design similar to that of an ARM processor, and Intel must use the latest 22 NM manufacturing process.

2, 64-bit computing for 64-bit computing, arm and Intel also have some notable differences. Intel does not develop a 64-bit version of the x86 instruction set. The 64-bit instruction set, known as x86-64 (sometimes referred to as x64), is actually developed by AMD. Intel wants to do 64-bit computing, knowing that if the new architecture is less efficient if it evolves from its 32-bit x86 architecture, it has a new 64-bit processor project named IA64. This creates an Itanium series of processors.

And arm saw the mobile device for 64-bit computing needs, in 2011 released the ARMV8 64-bit architecture, this is for the next generation of ARM instruction set architecture work for several years after the crystallization. In order to develop a concise 64-bit architecture based on the original principles and instruction set, ARMV8 uses two execution modes, AArch32 and AArch64. As the name suggests, a run of 32-bit code, a run of 64-bit code. The ingenious point of arm design is that the processor can switch seamlessly between the two modes in operation. This means that the decoder for the 64-bit instruction is completely new, with no 32-bit instructions, and the processor can still be backwards compatible.

3, heterogeneous computing arm of the big. The little architecture is an innovation that Intel cannot replicate for a while. In big. In the little architecture, processors can be of different types. Conventional dual-or quad-core processors contain the same 2 cores or 4 cores. A dual-core Atom processor has two identical cores that provide the same performance and have the same power consumption. ARM has introduced heterogeneous computing to mobile devices via big.LITTLE. This means that the cores in the processor can have different performance and power consumption. When the device is working properly, use a low-power core, and when you run a complex game, you use a high-performance kernel.

What is this? When designing a processor, consider the adoption of a large number of technical designs that determine the processor's performance and power consumption. When an instruction is decoded and ready to execute, both Intel and ARM processors use pipelining, which means that the decoding process is parallel.

In order to execute instructions more quickly, these pipelining can be designed to allow instructions to be executed not in the order in which they are programmed (disorderly execution). Some ingenious logical structures can determine whether the next instruction relies on the results of the current instruction execution. Intel and ARM provide random execution logic structure, it is conceivable that this structure is very complex, complex means more power consumption.

So why is arm's power consumption much less than X86? This is related to another factor, that is design.

Design is divided into front-end and back-end design, the front-end design embodies the structure of the processor, the simplification of the instruction set and the complexity of the instruction set is reflected through the front-end design. Back-end design to deal with voltage, clock and other problems, is a direct factor in power consumption. Of course, any of these will make the clock and power-controlled modules not working. The difference is that gated clocks have a shorter recovery time and a longer power control. In addition, if a single instruction uses multiple modules of the function, in the recovery function, it is not the slowest module of time, but may be a few modules time added, because this involves a power order problem, that is, restore the work of the module is in order, do not follow this order, can not be restored. In this order, the total recovery time is very long.

So at the back end, you can get a conclusion that, in order to save power, you can turn off some of the processor modules that are temporarily unavailable. But it can not be easily closed, otherwise, once needed, the recovery will allow a long time to complete a command, the overall performance is obviously reduced. In addition, the child module's gated clock and power switch are usually determined when designing the circuit, which is transparent to the operating system and cannot be optimized by software.

Look at the front end again. ARM's processor has a characteristic, is disorderly order execution ability inferior X86. In other words, the user is using the computer, his operation is random, unpredictable, resulting in instructions also unpredictable. X86 in order to enhance the processing ability in this case, the execution of the ordered order is enhanced. In addition, X86 also enhances the multi-threaded capabilities of the single core. The disadvantage of this is that the Processor sub module cannot be effectively shut down and restored because once it is turned off, the recovery is slow, resulting in low performance. In order to maintain high performance, most of the modules have to be kept open, and the clock stays switched. The direct consequence of this is high power consumption. And arm's instructions are strong in the order of execution, and rely on multi-core rather than single-core multithreading to execute. This is easy to keep the module and clock signal closed, obviously more power-saving.

How is arm and X86 developing now?

About X86 architecture and ARM architecture both of which will be unified market dispute has been, but some people say that the two are not comparable, X86 can not do arm power, and arm can not do X86 performance. Now ARM architecture has the ability to enter the server chip, many chip research and development enterprises have adopted the ARM architecture research and development server chip will undoubtedly promote its prosperity, 2015, a use of ARM architecture of the Windows 10 tablet, which is currently exposed to the world's first X86 architecture, A tablet product that runs a Windows system.

With the mobile network and the Internet convergence increasingly obvious, arm development of the background data center is the trend, so rather than arm is more like bite, whether arm or Intel, both sides have no retreat to speak.