Power on reset, shift, decode, execute, repeat.
Intel loves complexity, which is why they invented USB: another tree killer.
The processor doesn't do anything. In all that silicon and its pages of documentation, you can't even find a parser for assembly language; you need software for that.
In spite of 4000+ pages of documentation, printing "Hello, world" on a screen requires additional hardware, and a very detailed program. Want a linked list, or regex pattern matching? Not in the 4000 pages; write the code.
And this is just the architecture manuals software developers. This is not documentation of the actual silicon. What it contains:
This document contains all seven volumes of the Intel 64 and IA-32 Architectures Software Developer's Manual: Basic Architecture, Instruction Set Reference A-L, Instruction Set Reference M-Z, Instruction Set Reference, and the System Programming Guide, Parts 1, 2 and 3. Refer to all seven volumes when evaluating your design needs.
Instruction set references and system programming guide; that's it!
Note also that this is not the programming documentation for a system on a chip (SoC). There is nothing in this 4000+ page magnum opus about any peripheral. No serial ports, no real time clocks, no ethernet PHY's, no A/D D/A converters; nothing. Just CPU.