Computer Instruction Set CISC

When new CPUs are introduced, merchants will first describe it as a RISC instruction set. What does this mean? How many CPU features do you know from this description?

Complex Instruction Set Computer (CISC)

In the long term, the improvement of computer performance is often achieved by increasing the complexity of hardware. with the integrated circuit technology. in particular, the rapid development of the very large scale integrated circuits technology, in order to facilitate software programming and improve the speed of program operation, hardware engineers are constantly adding instructions that can implement complex functions and a variety of flexible addressing methods. even some commands support complex operations after advanced language statements are classified. as the hardware becomes more and more complex, the cost also increases accordingly. to implement complex operations, the microprocessor provides programmers with functions similar to various registers and machine commands. the microprogram stored in the read-only memory (ROM) is also used to implement its strong functions. Proud to perform a series of basic command operations after analyzing each command to complete the required functions, this design type is called the Complex Instruction Set Computer-CISC structure. generally, CISC computers contain at least 300 commands, and some contain more than 500 commands.

Reduced Instruction Set Computer (RISC)

Computers using complex command systems have a strong ability to process advanced languages. this is helpful for improving computer performance. when computer design goes along this path. some people do not follow the stream. they looked back at the path they had taken and began to doubt this traditional approach: IBM did not have jhomasi in Yorktown, New York. wason Research Center organized forces to study the rationality of command systems in 1975. at that time, it was felt that the increasingly complex command system was not easy to implement. it may also reduce system performance. in 1979, a group of scientists headed by Professor Paterson started the study at the American University of California, Berkeley. the results show that CISC has many disadvantages. first. in this computer. the usage of various commands varies greatly: the 80% commands used in the calculation process of a typical program. accounts for only 20% of the Instruction System of one processor. in fact, the most frequently used commands are the simplest commands, such as getting, storing, and adding. in this way, the long-term commitment to the design of complex command systems is actually to design a processor that is rare to use in practice. at the same time. complex command systems will inevitably bring about structural complexity. this not only increases the design time and cost, but also easily leads to design errors. in addition. although the current level of the very high level of the technology, it is difficult to make all the CISC hardware on a single chip, which also hinders the development of a single chip computer. in CISC, many complex commands require extremely complex operations. Most of these commands are directly revised in a certain advanced language, which leads to poor universality. because of the second-level microcode execution method, it also reduces the running speed of simple command systems that are frequently called. therefore. these disadvantages of CISC. paterson and others proposed the idea that the command system should only contain a small number of commands that are frequently used. and provide some necessary commands to support the operating system and advanced language. A computer developed in accordance with this principle is called a simplified instruction set computer (AES) structure. short.

Difference between CISC and RISC

We often talk about topics related to "PC" and "Macintosh", but how many people know that the PC series with intel X86 as the core is based on the CISC architecture, while Apple's Macintosh is based on the structure of the RISC system. What is the difference between the CISC and the Proteus?

From the hardware point of view, CISC processes the instruction set of unequal length. It must separate the instruction set of unequal length. Therefore, a large amount of processing work is required when executing a single instruction. In contrast, assume that the CPU runs a short instruction set with a high speed and stable performance when executing commands. Therefore, in the aspect of parallel processing, the number of commands is much better than that of CISC. The number of commands that can be executed by a single command can be divided into several processes or threads, which can be executed by multiple processors at the same time. Due to the execution of a simplified instruction set, the manufacturing process is simple and cost-effective.

From the software perspective, CISC runs DOS and Windows operating systems that we know well. It also has a large number of applications. Because more than 65% of software vendors around the world are responsible for the PC and Its compatible machine services based on the CISC architecture, the well-known Microsoft is one of them. But in this regard, he seems a little weak. Although DOS and Windows can also be run on the server Load balancer, a translation process is required, so the operation speed is much slower.

At present, CISC is gradually moving towards the integration of server Threat Management Framework. Pentium Pro, nx586, and K5 are the most obvious examples. Their kernels are all based on the server Threat Management Framework. After receiving the CISC command, they break it down and classify it into a number of them. This allows them to execute multiple commands at the same time. It can be seen that the next generation of CPU will be integrated with CISC and RISC technologies, and the two will complement each other in terms of software and hardware.

After reading the above content, I understand that:

CISC usually uses multiple system clocks to execute a single command. For example, 51 Single-Chip Microcomputer uses 12 clock cycles to complete the process of obtaining, analyzing, and executing a single command, instead of using only one clock cycle to execute one instruction, the server generally uses a pipeline structure, that is, to execute one instruction and take the next instruction, which is completed within the same clock cycle.

Computer Instruction Set CISC