Stories with Tag Digital Logic

• Build an 8-bit computer from scratch (2016)

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  Posted: 2025-03-31 11:29:34

  Verbose tl;dr

  This blog post chronicles a personal project to build a functioning 8-bit computer from scratch, entirely with discrete logic gates. Rather than using a pre-designed CPU, the author meticulously designs and implements each component, including the ALU, registers, RAM, and control unit. The project uses simple breadboards and readily available 74LS series chips to build the hardware, and a custom assembly language and assembler are developed for programming. The post details the design process, challenges faced, and ultimately demonstrates the computer running simple programs, highlighting the fundamental principles of computer architecture through a hands-on approach.

  This comprehensive blog post, "Build an 8-bit computer from scratch," chronicles the author's ambitious journey of designing and constructing a fully functional 8-bit computer entirely from discrete logic gates. The project, undertaken in 2016, begins with a deep dive into the fundamental building blocks of digital logic, including AND, OR, XOR, and NOT gates, meticulously explaining their behavior and symbolic representation. The author then progresses to building more complex components, such as adders, multiplexers, and flip-flops, illustrating their design and functionality using detailed diagrams and explanations. The construction process is thoroughly documented, demonstrating how these individual components are interconnected to form larger modules.

  The central processing unit (CPU), the heart of the computer, is explained in detail, covering its architecture, instruction set, and the flow of data and control signals within the system. The author meticulously describes the design of the arithmetic logic unit (ALU), the control unit, and the registers, elucidating how they cooperate to execute instructions. Memory management is another key aspect of the project, with the blog post explaining the implementation of Random Access Memory (RAM) and Read-Only Memory (ROM), detailing how data is stored and retrieved.

  The post also covers the design and implementation of input and output (I/O) mechanisms, enabling the computer to interact with the external world. This involves creating a simple display for outputting information and a mechanism for inputting instructions and data. Furthermore, the author discusses the process of developing software for the computer, including the creation of a simple assembler and the challenges of programming at such a low level.

  Throughout the project, the author emphasizes the importance of understanding the underlying principles of computer architecture, rather than simply assembling pre-built components. The blog post aims to provide a clear and comprehensive understanding of how a computer functions at its most basic level, demonstrating the complex interplay of hardware and software. The detailed explanations, accompanied by numerous diagrams and schematics, make the intricate workings of the computer accessible to a wide audience, even those without a deep background in electronics or computer science. The author's journey serves as a testament to the power of understanding fundamental principles and the satisfaction of building something complex from the ground up.

  • 8-bit computer
  • Computer Architecture
  • DIY computer
  • Hardware
  • Electronics
  • from scratch
  • Tutorial
  • Ben Eater
  • breadboard computer
  • Digital Logic
  • Computer Engineering

  Summary of Comments ( 45 )
  https://news.ycombinator.com/item?id=43533715

  Verbose tl;dr

  HN commenters discuss the educational value and enjoyment of Ben Eater's 8-bit computer project. Several praise the clear explanations and well-structured approach, making complex concepts accessible. Some share their own experiences building the computer, highlighting the satisfaction of seeing it work and the deeper understanding of computer architecture it provides. Others discuss potential expansions and modifications, like adding a hard drive or exploring different instruction sets. A few commenters mention alternative or similar projects, such as Nand2Tetris and building a CPU in Logisim. There's a general consensus that the project is a valuable learning experience for anyone interested in computer hardware.

  The Hacker News post "Build an 8-bit computer from scratch (2016)" has a moderate number of comments, discussing various aspects related to the linked Eater.net article about building an 8-bit computer. Several commenters express excitement and nostalgia for the Ben Eater series, praising its clarity and educational value. They appreciate the hands-on approach and the way it demystifies computer architecture.

  A key discussion revolves around the benefits of such projects for learning. Commenters note how building a computer from basic components provides a deep understanding of how computers work at a fundamental level, contrasting this with higher-level programming or software development. Some commenters share their own experiences of following the tutorial and the insights they gained.

  Some comments delve into the specifics of the project, such as the choice of components, the complexity of the instruction set, and the potential for expansion. There's mention of alternative or similar projects like Nand2Tetris and From Nand to Tetris, comparing and contrasting their approaches to teaching computer science concepts.

  A few commenters also touch on the broader implications of understanding computer architecture, arguing it fosters a greater appreciation for the complexity and ingenuity of modern computing. They emphasize the importance of this knowledge in a world increasingly reliant on technology. Some express the sentiment that this type of project can be inspirational for aspiring engineers and programmers. Finally, there's some light discussion about the cost and time commitment involved in undertaking such a project.

• Simple CPU Design

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  Posted: 2025-01-22 15:07:26

  Verbose tl;dr

  This blog post details a simple 16-bit CPU design implemented in Logisim, a free and open-source educational tool. The author breaks down the CPU's architecture into manageable components, explaining the function of each part, including the Arithmetic Logic Unit (ALU), registers, memory, instruction set, and control unit. The post covers the design process from initial concept to a functional CPU capable of running basic programs, providing a practical introduction to fundamental computer architecture concepts. It emphasizes a hands-on approach, encouraging readers to experiment with the provided Logisim files and modify the design themselves.

  This blog post, titled "Simple CPU Design," meticulously details the process of designing a rudimentary Central Processing Unit (CPU) using readily available, cost-effective components like an Arduino Mega. The author emphasizes the educational value of the project, highlighting its potential to provide a practical understanding of fundamental computer architecture principles. The design centers around a simplified Harvard architecture, which means the CPU uses separate memory spaces for instructions and data. This separation simplifies the design and allows for concurrent access, potentially increasing processing speed.

  The core functionality of the CPU is explained through a series of interconnected modules, including an Arithmetic Logic Unit (ALU), responsible for performing arithmetic and logical operations; a Control Unit (CU), which fetches instructions from memory and decodes them to control the other components; program memory, holding the instructions to be executed; data memory, for storing data used in computations; and registers, which serve as fast, temporary storage locations within the CPU. The interplay between these modules is illustrated through detailed diagrams and explanations of the data flow.

  The ALU, a crucial component, supports a limited set of arithmetic and logical operations, including addition, subtraction, bitwise AND, and bitwise OR. The Control Unit, designed using a finite state machine approach, fetches instructions from program memory and decodes them into control signals that dictate the operation of the ALU, data memory, and registers. The instruction set architecture (ISA) is purposely kept simple, with a small number of instructions that encompass basic arithmetic, logical, memory access, and control flow operations.

  The blog post provides comprehensive schematics, illustrating the connections between the various components and the flow of data within the CPU. It also includes the Arduino code used to emulate the CPU's functionality, demonstrating the logic behind each operation. The code serves as a concrete implementation of the theoretical design principles discussed. Furthermore, the author emphasizes the modularity of the design, suggesting possibilities for expansion and improvement, such as increasing the size of memory or adding more complex instructions to the ISA. This iterative approach reinforces the learning process, encouraging experimentation and further exploration of CPU design principles.

  The author acknowledges the limitations of the simplified design compared to modern CPUs, particularly in terms of performance and complexity. However, they stress the project’s pedagogical value, arguing that it offers a tangible and accessible way to grasp the core concepts of computer architecture. This simplicity allows for a focused understanding of the essential building blocks of a CPU without the overwhelming complexity of modern processors. The project is presented as a stepping stone towards more advanced exploration of computer architecture and digital design.

  • CPU Architecture
  • Computer Architecture
  • CPU Design
  • Hardware Design
  • Digital Logic
  • Computer Engineering
  • Processor Design
  • Instruction Set Architecture
  • ISA
  • Microarchitecture
  • Hardware
  • VLSI Design
  • Computer Organization

  Summary of Comments ( 0 )
  https://news.ycombinator.com/item?id=42793597

  Verbose tl;dr

  HN commenters largely praised the Simple CPU Design project for its clarity, accessibility, and educational value. Several pointed out its usefulness for beginners looking to understand computer architecture fundamentals, with some even suggesting its use as a teaching tool. A few commenters discussed the limitations of the simplified design and potential extensions, like adding interrupts or expanding the instruction set. Others shared their own experiences with similar projects or learning resources, further emphasizing the importance of hands-on learning in this field. The project's open-source nature and use of Verilog also received positive mentions.

  The Hacker News post titled "Simple CPU Design" linking to simplecpudesign.com has generated a moderate discussion with a number of insightful comments. Several commenters praise the clarity and accessibility of the resource, finding it a valuable introduction to CPU architecture. One user appreciates its focus on the fundamentals, contrasting it with more complex designs often encountered in university settings. They highlight how the tutorial breaks down the concepts into manageable steps, making it easier to grasp the overall picture.

  Several users discuss their own experiences with similar projects, often mentioning their use of FPGAs and VHDL or Verilog for implementation. They share specific challenges and solutions encountered during their learning process, creating a sense of shared experience among those interested in building their own CPUs. One commenter recounts their project of building a CPU on an FPGA and connecting it to a PS/2 keyboard, emphasizing the rewarding feeling of seeing their creation interact with physical hardware.

  The practicality of the design is also a point of discussion. Some commenters note the limitations of such a simple CPU, particularly its lack of pipelining and other performance-enhancing features. However, others argue that the simplicity is the point, allowing for a deeper understanding of the core principles before moving on to more complex designs. This echoes the sentiment that the tutorial is an excellent starting point, laying a solid foundation for further exploration.

  There's also some discussion around potential enhancements and modifications to the simple CPU design. Ideas include adding interrupts, implementing a more complex instruction set, and exploring different memory architectures. This demonstrates the engagement of the commenters and their interest in pushing the design further.

  A recurring theme is the educational value of the resource. Many users express their enthusiasm for finding a clear and concise explanation of CPU design, often contrasting it with more academic or overly technical resources. They appreciate the author's approach of starting with the basics and gradually building complexity. One user even suggests using the tutorial as a teaching tool for introductory computer architecture courses.

  Finally, there are a few comments discussing the choice of Logisim, the digital logic simulator used in the tutorial. While some find it suitable for the purpose, others suggest alternative simulators like Digital, pointing to their advantages in terms of features and usability. This discussion highlights the variety of tools available for those interested in exploring digital logic design.