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.
VexRiscv is a highly configurable 32-bit RISC-V CPU implementation written in SpinalHDL, specifically designed for FPGA integration. Its modular and customizable architecture allows developers to tailor the CPU to their specific application needs, including features like caches, MMU, multipliers, and various peripherals. This flexibility offers a balance between performance and resource utilization, making it suitable for a wide range of embedded systems. The project provides a comprehensive ecosystem with simulation tools, examples, and pre-configured configurations, simplifying the process of integrating and evaluating the CPU.
Hacker News users discuss VexRiscv's impressive performance and configurability, highlighting its usefulness for FPGA projects. Several commenters praise its clear documentation and ease of customization, with one mentioning successful integration into their own projects. The minimalist design and the ability to tailor it to specific needs are seen as major advantages. Some discussion revolves around comparisons with other RISC-V implementations, particularly regarding performance and resource utilization. There's also interest in the SpinalHDL language used to implement VexRiscv, with some inquiries about its learning curve and benefits over traditional HDLs like Verilog.
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https://news.ycombinator.com/item?id=42793597
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.