计算机指令集_计算机科学组织| 指令集及其类型

计算机指令集

指令系统 (Instruction Set)

An instruction set can be defined as a group of instruction that a processor can execute to perform different operations. On the basis of complexity and the number of instruction used the instruction set can be classified as

指令集可以定义为处理器可执行以执行不同操作的一组指令。根据复杂性和使用的指令数量，可以将指令集分类为

Complex Instruction set

复杂指令集
Reduced Instruction set

精简指令集

1)复杂指令集 (1) Complex Instruction set)

The complex instruction set is the set of instruction which includes very complex and large number of instructions. The number of instruction in this set varies from 100 to 250. The instruction in this set is mostly memory based instruction, which involves frequent to the memory. The complex instruction set makes use of a large number of addressing modes because of the frequent references to register as well as memory. The instruction in this instruction takes a lot of time because the instructions format which is not limited to only 32 bit.

复杂指令集是包括非常复杂和大量指令的指令集。该集中的指令数量从100到250不等。该集中的指令主要是基于内存的指令，涉及到内存频繁。由于频繁引用寄存器和存储器，因此复杂的指令集使用了大量的寻址模式。该指令中的指令要花费很多时间，因为指令格式不仅限于32位。

The complex which makes use of complex instruction set is called Complex Instruction set Computer (CISC). The instruction set of CISC has a large number of instruction and for each instruction type.

利用复杂指令集的复合体称为复杂指令集计算机(CISC)。对于每种指令类型，CISC的指令集都有大量指令。

Advantages of Complex Instruction Set

复杂指令集的优点

There is no need to invent an instruction set for each new design. The instruction set of the predecessor is used by the new user.

无需为每个新设计发明一套指令集。新用户使用前身的指令集。
A program written in CISC require less memory space as the code is confined to less number of instruction.

用CISC编写的程序需要较少的存储空间，因为代码仅限于较少的指令数。
CISC makes the job of a computer easier by facilitating the implementation of high-level language constructs.

通过促进高级语言结构的实现，CISC使计算机的工作更加轻松。

Disadvantages of Complex Instruction set

复杂指令集的缺点

The inheritance of old instruction into new processor increase the complexity.

将旧指令继承到新处理器中会增加复杂性。
Many CISC instructions are not frequently used.

许多CISC指令不经常使用。
CISC command is translated into a large number of lines of microcode which makes the CPU processing slower.

CISC命令被翻译成大量的微代码行，这使CPU处理速度变慢。
CISC system has a complex hardware, so they require more times for designing.

CISC系统具有复杂的硬件，因此需要更多的时间进行设计。

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2)精简指令集 (2) Reduced Instruction Set)

The reduced instruction set refers to a set of instruction that contains very few instructions ranging from 0 to 100. It comprises only those instruction that is frequently used by the processor for the execution of a program. The instruction is generally very simple to execute. The memory-based instruction includes the only load and stores instructions. The instruction in this instruction set has fixed length instruction format of 32 bits. An instruction format divides the bits of instructions into small group fields. Generally, an instruction has the following fields:

精简指令集是指包含很少的0到100范围内的指令的指令集。它仅包括处理器经常用于执行程序的那些指令。该指令通常很容易执行。基于存储器的指令仅包括加载和存储指令。该指令集中的指令具有固定长度的32位指令格式。指令格式将指令的位分成小组字段。通常，一条指令具有以下字段：

Opcode field

操作码字段

It represents the operations to be performed by the instruction.

它代表指令要执行的操作。
Operand field

操作数字段

It represents the data on which the operations are to be performed or the memory location or registers where the data is stored.

它表示要在其上执行操作的数据或存储该数据的存储器位置或寄存器。
Mode field

模式字段

It represents the method of fetching the operands stored at specified memory location or register.

它表示获取存储在指定存储位置或寄存器中的操作数的方法。

The comparison of RISC and CISC processor indicated that the RISC processor is always preferred over the CISC processor because of their compact size and small instruction set.

RISC和CISC处理器的比较表明，RISC处理器始终比CISC处理器更受青睐，因为它们具有紧凑的尺寸和小的指令集。

Advantages of Reduced Instruction set computer

精简指令集计算机的优势

The other advantages of RISC processor over the CISC processor are as follow:

RISC处理器相对于CISC处理器的其他优点如下：

In RISC processor the instructions are executed by decoding but in CISC processors, the instructions are executed by first and then translating them into equivalent microcode instructions. The conversion of instruction into microcode consumes a lot of space in the memory thereby reducing the speed of executions.

在RISC处理器中，指令是通过解码执行的，而在CISC处理器中，指令是先执行的，然后将其转换为等效的微码指令。将指令转换为微代码会占用内存中的大量空间，从而降低了执行速度。
The RISC processor executes an instruction in a single clock cycle, while the CISC processor requires multiple clocks cycles for the execution of an instruction.

RISC处理器在单个时钟周期内执行一条指令，而CISC处理器则需要多个时钟周期才能执行一条指令。

Disadvantages of Reduced Instruction set computer

精简指令集计算机的缺点

The only disadvantages of RISC in comparison to CISC is that the number of instructions required to perform an operation is comparatively large.

与CISC相比，RISC的唯一缺点是执行操作所需的指令数量相对较大。

翻译自: https://www.includehelp.com/cso/instruction-set-and-their-types.aspx

计算机指令集