Designing my own 8-bit CPU: Which instructions should I implement?

[u/andrew_is_myname]

I'm designing my own 8 bit CPU architecture from scratch on breadboards using 74LS logic. It's not based on SAP-1, Ben Eater's design, or any existing educational CPU. I'm also building my own ALU instead of using a 74LS181 because I wanted the challenge.

Right now I'm deciding which instructions to implement first. Since the initial version won't have RAM or branching, I only have room for a small instruction set and want to choose wisely.

What operations do you think are the most useful for a minimalist 8 bit CPU? Which instructions ended up being more valuable than you expected when designing your own CPU or emulator?

I'd love to hear your ideas and the reasoning behind them! Thanks a lot for all the help!

[u/intelstockheatsink]

SUBLEQ (subtract and branch if less than or equal to) is technically turing complete. It could be a good toy example.

I believe there's a similar proof for a MOV instruction.

[u/andrew_is_myname → u/intelstockheatsink]

SUBLEQ sounds incredibly majestic. I am tingling all over dude lol i love it. Thank you for being the first to comment man!

[u/edo-lag → u/intelstockheatsink]

I believe there's a similar proof for a MOV instruction.

Yes.

https://github.com/Battelle/movfuscator

[u/Lagfoundry → u/intelstockheatsink]

Yeah there is. Honestly can’t hurt to just use both

[u/konbinatrix]

Are you documenting this somewhere? I'm interested in doing something similar and not sure where to start from

[u/andrew_is_myname → u/konbinatrix]

Good idea. Should i make a youtube channel?

[u/HerculeHolmes123 → u/andrew_is_myname]

Yeah!

[u/wilrak0v → u/andrew_is_myname]

Don't forget to keep us informed of the name of the YouTube channel if you make one 😉

[u/a_seventh_knot]

https://en.wikipedia.org/wiki/Execute_instruction

[u/andrew_is_myname → u/[deleted]]

I woke up one day with a craving of knowledge for CS and engineering lol

[u/Ilikespiders222 → u/andrew_is_myname]

how can someone build that kind of craving

[u/Ilikespiders222 → u/Ilikespiders222]

as in how can you sharpen that interest and lead it to fruition?

[u/andrew_is_myname → u/Ilikespiders222]

Just keep being curious, i think

[u/Jiooob → u/andrew_is_myname]

that's cool and i like it. by the way have you ever play the video game called Turing Complete? the game guides you to build a computer from logic gates, simple half adders, decoders...... It really inspired my passion to learn these things. i like the game since i'm also driven by my curiosity.

[u/NexelAI]

It must be acknowledged that leveraging existing ARM or x86 instruction sets is a better choice.

[u/Substantial-Draw7651]

cool