> Surely we are way past the point where someone knows how the whole thing works, all the way down.
I've met a few people who can rightfully lay claim, but yeah, an incredibly rare set of skills.
That said, there is a recent revival in building systems from the ground up. While you can't manufacturer your own transistors, it is quite possible to understand everything from simple logic gates to ALUs to older style CPUs and memory buses.
I built a toy CPU in software once as an exercise. I started with "class Transistor" (wrapping an AND op) and "class Wire" (wrapping a boolean), and wired them together incrementally to make gates, flipflops, registers, etc.
I eventually got a fully-functioning 32-bit cpu with instruction pipelining, two levels of cache, DMA input/output, an asynchronous bus, a custom assembly language with an assembler written in python, and got the Game of Life running on it.
I've met a few people who can rightfully lay claim, but yeah, an incredibly rare set of skills.
That said, there is a recent revival in building systems from the ground up. While you can't manufacturer your own transistors, it is quite possible to understand everything from simple logic gates to ALUs to older style CPUs and memory buses.