When I worked on my Commodore 65xx computers, I intimately understood their hardware architecture, the Page Zero layout, the general layout of RAM/ROM, PEEK/POKE registers that mattered, CPU operations, and I had a general knowledge of assembly language. And most of this was documented in the user manuals themselves; the only other stuff I read was "Compute!'s Gazette".

When I received my first IBM PS/2 in 1989, I hardly knew any of this stuff. I didn't know any x86 assembly, I didn't know how DOS laid out memory or how the INT routines accessed devices. My computer overnight turned into a black box. I didn't program it in BASIC, I just loaded games and applications on it.

This sort of system opacity drove me rather crazy, and soon I was in college studying Unix and systems architecture again. I didn't waste any time deleting DOS/Windows and replacing it with Minix.