CPU Architecture Lecture Notes

Introduction to CPUs

• CPUs (Central Processing Units) are present in various devices: laptops, grocery store machines, cars, etc.
• CPUs play a crucial role in computation and enable significant advancements in fields like art and science.
• Speaker: Boyd Phelps, experienced in chip design at Intel.
• Aim of the lecture: To enhance understanding of CPU architecture and inspire future innovations.

Lecture Structure

• Module 1: A brief history of CPU architecture, computing abstraction layers, and instruction set architecture (ISA).
• Module 2: Building blocks of CPUs, focusing on front-end and back-end, and an introduction to caching.

What is a CPU?

• The CPU is the brain of the computer, managing computation between memory and output devices.
• It runs operating systems, applications, and processes various workloads.
• CPUs are general-purpose and flexible.

Moore's Law

• Moore's Law: The observation that the number of transistors per unit area doubles approximately every two years.
• This trend has led to increased functionality and efficiency in CPUs over time.
• Transition from large, complex systems to compact, powerful microprocessors.

Historical Context

• Early computers (e.g., ENIAC) were large, slow, and used vacuum tubes.
• The von Neumann Architecture (John Von Neumann, late 1940s): A significant advancement that introduced:
  • Separation of memory and processing units.
  • A four-step instruction cycle: Fetch, Decode, Execute, Store.

Evolution of Technology

• 1950s: Introduction of semiconductor-based transistors, replacing vacuum tubes.
• 1968: Robert Noyce and Gordon Moore founded Intel; introduced Intel 4004 (1971): First general-purpose programmable processor.
• Intel 8080 and 8086 introduced further advancements in microprocessor technology.

Key Concepts in CPU Design

• Binary System: All data in digital computers represented in binary (0s and 1s).
• Computing Abstraction Layers: Building complex systems through layers starting from fundamental components (atoms -> transistors -> logic gates).

Logic Gates and Functional Blocks

• Basic logic operations: AND, OR, NOT using transistors as switches.
• Functional blocks include arithmetic logic units (ALUs), multiplexers, and more.
• Microarchitecture: Combining processing elements to form a CPU that executes instructions.

Instruction Set Architecture (ISA)

• The ISA defines the operations that can be performed in hardware and acts as a bridge between software and hardware.
• Various ISAs (e.g., x86, ARM, MIPS) guide instruction execution and programming.
• Compilers transform high-level language code into machine code based on the ISA.
• Instructions consist of an opcode and operands, detailing operations and data.

Importance of ISA in Modern CPUs

• Modern ISAs evolve with extensions for efficiency and performance.
• Thousands of instructions are supported, primarily for arithmetic, logical, memory, and control operations.
• ISAs provide a crucial framework for CPU design, affecting software experience and performance.

Conclusion and Preview of Part 2

• Part 2 will elaborate on microarchitecture, instruction cycles, CPU front-end and back-end, and caching.
• Encouragement for students to engage with the material and envision their role in shaping the future of CPU technology.