CSSC - EP.0 Teaser: How About Designing a Computer? - Stack CPU

As the semester drew to a close, each of us was required by our teacher to submit a project for the Digital Circuit Design course, assembled using at least the 74 series ICs. That’s when a bold idea suddenly struck me: why not design a computer?

I’ve long been deeply fascinated and inspired by Uxn, created by Hundred Rabbits. After graduating junior high, I also personally assembled Ben Eater’s Breadboard CPU (only partially, as it was never completed due to missing parts and has been gathering dust). So it suddenly occurred to me: Uxn was originally designed for easy implementation on various platforms, but what if it could be implemented on actual hardware?

This idea was bold, but with only a week left until the assignment deadline, I didn’t overthink it. After confirming that a stack pointer could be implemented with a simple counter, I hastily built Ben Eater’s ALU, Register A, and Register B, and soldered them onto a perfboard to prevent loose connections during transport.

However, as time went on and my understanding of the project deepened, I gradually began to realize that it wasn’t as simple as I had initially imagined. This is why the project is called CSSC - Composable Super Simple Computer. To allow for rolling updates and corrections to any future designs, I will incorporate many modifiable elements into the subsequent implementations, enabling more combinations and applications down the line.

But it was also through this project that I became aware of the IC shortage in Taiwan (especially in the south) and the discontinuation of many components. Therefore, the term ‘Composable’ in this project doesn’t just refer to the high reusability and modularity of the components. For the future development of the project, it also addresses the challenge of finding replacements for many parts after they are discontinued – whether we can use more advanced yet highly customizable components (like MCUs/FPGAs) to implement replacements for chips that are no longer produced. (Although this might sound a bit silly, it’s what I’ve considered so far.)

This project will also follow a rolling update approach. If any new discoveries or errors are found, previous articles may be directly modified (or even deleted). Some content might also remain in draft status for a long time before being published. (While a dev blog’s primary format won’t be overly formal or rigid, I still aim for the content to be as complete and cohesive as possible, not fragmented.)

As I’m still a university student, I’m continuously learning throughout this project. Any new discoveries will be introduced in future blog posts! (=ﾟωﾟ)ﾉ

Preview

In the very next post, I’ll briefly explain the implementation details and ideas behind the ALU, Register A, and Register B. Subsequently, I’ll provide more introductions and explanations regarding many other details, research, and ideas related to this project.

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