What is CISC (Complex Instruction Set Computing)? скачать в хорошем качестве

What is CISC (Complex Instruction Set Computing)?

CISC, which stands for Complex Instruction Set Computing, refers to a type of computer architecture where instructions that the processor can execute are more numerous and can perform a variety of low-level operations within a single instruction. CISC architectures contrast with RISC (Reduced Instruction Set Computing) architectures, which have a smaller set of simpler instructions. Key characteristics of CISC architecture include: Rich Instruction Set: CISC architectures have a large and complex set of instructions. Each instruction can perform multiple low-level operations, allowing for more functionality within a single instruction. Variable-Length Instructions: Instructions in CISC architectures can have variable lengths. Some instructions might be very simple, while others can be more complex, depending on the operation they are designed to perform. Hardware Emphasis: CISC architectures often rely on complex hardware to execute instructions. This contrasts with RISC architectures, which tend to shift complexity from hardware to software. Memory Access Modes: CISC architectures typically support various addressing modes for memory access, providing flexibility in how operands are specified. Built-in Specialized Instructions: CISC architectures often include built-in instructions for commonly used operations, such as string manipulation, multiplication, and division. This can reduce the number of instructions required to perform certain tasks. Microprogramming: CISC processors often use microcode to implement complex instructions. Microcode is a set of instructions at a lower level of abstraction that the processor uses to execute the higher-level machine instructions. Examples of CISC architectures include the x86 architecture, which is widely used in personal computers, and the Motorola 68k architecture, which was used in early Apple Macintosh computers. While CISC architectures have the advantage of providing more functionality within a single instruction, they can also be more challenging to design and may have longer clock cycles compared to simpler RISC architectures. The trade-offs between CISC and RISC architectures have been a topic of ongoing debate in computer architecture design.