Yeah, it's helpful to remember that games in the early 90s at least would have been expected to run on a 486, which were still very widespread, and the 486 was neither superscalar nor out of order. It was pipelined (the main difference between a 486 and a 386) but it was still at that time simple to reason about how long your instructions would take. And there was no speedstep or any of that stuff yet.
This is so different from the current state of affairs.
Code for the CPU might get optimized beyond recognition, vectorized, executed out of order, ...
The shader code I write these days is translated to a whole list of intermediate formats across different platforms, maybe scheduled in a jobs system, then handed to graphics drivers which translate it to yet another format...
