What would you recommend as a good primer (textbook; website; manual; whatever) that would give someone with limited experience enough knowledge to avoid making that mistake and others like it?
I think Peter means the IBM PC architecture: the legacy layer on layer from the original IBM PC to modern laptops. To a first approximation, Coreboot can be considered an attempt to replace a big chunk of it with free software, so I'd guess most people on this list would never confuse the Programmable Interrupt Controller with the Microchip PIC CPU. After Coreboot hands over control to the OS kernel, it's really amazing how much abstraction hides the reality of the system from the OS. (And then the OS hides even more details from userspace, and so forth.)
To directly answer what you asked, start here: http://wiki.osdev.org/Main_Page - it may take a while, especially if you're not the intended audience (writing a custom OS from scratch), but it's a good overview.