Panthera: Ampere's CPU Performance Model

> Panthera represents low-background steel for computer systems. It is an end-to-end, industrial-grade performance model conceived, designed, and hand-crafted entirely by human architects before the era of generative AI. This repository represents over 8 years of work and 6000 individual git commits by 45 people. By making this human-authored codebase public, we hope it serves as a trusted, high-watermark reference for human engineers and future automated hardware-modeling tools alike.

This is a cycle accurate simulator. It takes a list of instructions and simulates how long it would take to actually execute those instructions. In addition it keeps track of counters for various things (cache misses, interrupts, etc). Correlation refers to making sure the counter values reported by the sim are within some ballpark of the same values on a real chip. Cycle accurate sims are used for architecture research (trying out new features) as well as pre-silicon software work - chip isn't taped out but you want to start building a compiler. They are generally very slow (1000x slower than running on device) because they are generally written by HW people who have no idea how to write fast code. I would be interested to know how fast this one is.

Too bad they can't use this to design a high performance core.