I'd recommend learning how transformers work, and the concept of temperature. I don't think I need to cite information that is broadly and readily available, but here:
https://medium.com/google-cloud/is-a-zero-temperature-determ...
I also qualified the requirement of needing the same hardware, due to FP shenanigans. I could further clarify that you need the same stack (pytorch, tensorflow, etc)
This gcc script that I created below is just as "deterministic" as an LLM. It produces the same result every time. Doesn't make it useful though.
Also, how transformers work is not a spec of the LLM that anyone can use to learn how LLM produces code. It's no gcc source code.