Below you will find pages that mention the tag “816cpu”
It’s alive – not yet a valid program, it is just executing NOPs right now.
I made good progress on my CPU design in the last two days. It’s starting to come alive.
Yesterday I found Logisim-evolution, a free digital circuit simulator. Just the tool I need for my CPU project. Now I’m in the progress of designing my circuit in it. Looks good so far. Found it via this youtube video: Intro to Logisim Evolution, the free and oh-so-good logic simulation software.
The longer I’m working on my CPU design, the more I come to realize how simplified my understanding of how a CPU works actually is. Yes, I know how an ALU works and how to decode an instruction. But the moment you try to actually design your own architecture and add some nice features like function calling or interrupt, the hardware complexity explodes.
And the CPU got more complex once again. I just realized that I need more state and hardware to support my interrupt. Perhaps I should start removing features oO
The first simulated “program” running on my own instruction set. It takes more time than expected but from here it’s mostly repetition to finish it.
Designing a CPU you can actually still build with discrete elements and has a useful set of capabilities is quite complex project. And a significant trade-off between features and complexity. Just adding one register more makes it much more complicated than I expected.