cisc architecture | COA

Summary

This video provides an in-depth comparison between RISC (Reduced Instruction Set Computing) and CISC (Complex Instruction Set Computing) processors. It explains how CISC processors minimize the number of instructions per program by embedding multiple operations into single instructions, at the cost of requiring more clock cycles per instruction. CISC processors are typically used in desktop and laptop computers, where program size reduction is key. The video also highlights the characteristics of CISC, such as a large instruction set, complex instruction decoding, and varied addressing modes. Overall, it emphasizes the efficiency of CISC in handling large programs with reduced instruction lengths.

Takeaways

• 😀 RISC stands for Reduced Instruction Set Computer, while CISC stands for Complex Instruction Set Computer.
• 😀 CISC processors aim to minimize the number of instructions per program, ignoring the number of cycles per instruction.
• 😀 RISC processors are used in mobile devices like tablets and smartphones, while CISC processors are more common in desktop and laptop computers.
• 😀 The CISC processor design focuses on shortening the code length, leading to reduced memory usage for instructions.
• 😀 In CISC, the compiler has less work to do as the code length is relatively short compared to RISC processors.
• 😀 A key feature of CISC is that it can embed multiple operations into a single instruction to reduce the total number of instructions.
• 😀 CISC architecture reduces memory costs by minimizing the number of instructions per program and integrating operations into fewer instructions.
• 😀 The CISC processor architecture includes components like the control unit, instruction and data path, microprogrammed control unit, cache, and main memory.
• 😀 CISC processors support a variety of addressing modes and include a large number of instructions, which are minimized by embedding operations within single instructions.
• 😀 CISC instruction formats are of variable lengths, and executing one instruction may require several cycles, with complex instruction decoding logic.

Q & A

What is the main difference between RISC and CISC processors?

The main difference is that RISC processors focus on a reduced instruction set with simpler instructions that usually execute in one clock cycle, while CISC processors use a complex instruction set designed to minimize the number of instructions per program, often embedding multiple operations in a single instruction.

What type of devices typically use RISC processors?

RISC processors are commonly used in mobile devices such as tablets and smartphones due to their simplicity and efficiency in handling smaller, less complex tasks.

Which types of computers are most likely to use CISC processors?

CISC processors are primarily used in desktop and laptop computers where more complex operations are necessary.

How does the compiler work differently in CISC processors compared to RISC processors?

In CISC processors, the compiler has to do less work because the code length is shorter, thanks to the embedding of multiple operations in single instructions. In RISC, the code length tends to be longer and the compiler has to work harder to translate the program to machine code.

Why is less memory required for CISC processors?

CISC processors require less memory because they minimize the number of instructions per program, which leads to a shorter overall code length.

What is the primary design goal of CISC processors regarding instructions?

The primary design goal of CISC processors is to minimize the number of instructions per program by combining multiple operations into a single instruction.

What are the key components in the architecture of a CISC processor?

A CISC processor architecture typically includes a control unit, instruction and data paths, a microprogrammed control unit, cache, and main memory.

What is the impact of the complex instruction decoding logic in CISC processors?

The complex instruction decoding logic in CISC processors can make the processor design more intricate and slower at decoding instructions, but it allows for more powerful and varied instructions.

How do CISC processors manage memory costs in large programs?

CISC processors help manage memory costs by reducing the number of instructions needed, which decreases the overall memory required for storing the program, despite the need for larger storage in complex programs.

What is meant by 'variable length instruction formats' in CISC processors?

In CISC processors, instruction formats can vary in length, meaning that some instructions may be larger or smaller depending on the complexity of the operation being performed.