And I would love to encourage you to do so! If you're working for Cosmopolitan t...

And I would love to encourage you to do so! If you're working for Cosmopolitan then I'll be working hard to support you. There's a long history of depth to metal. Many people start off learning it by having fun with the old skool ibm pc boot process. Here's a gentle introduction: https://justine.lol/blinkenlights/realmode.html and https://github.com/jart/sectorlisp and http://reddit.com/r/osdev

Those concepts are implemented in the Cosmopolitan codebase here: https://github.com/jart/cosmopolitan/blob/master/ape/ape.S

That file runs a few hundred lines of old school assembly in order to bring us into the modern era. Towards the end of the file you'll notice it starts calling functions that are written in C which configure memory: https://github.com/jart/cosmopolitan/blob/master/libc/runtim...

After it configures memory, the ape.S file is able to call _start(). It also sets a bit in __hostos so that functions like write() know to use the serial port instead of issuing system calls: https://github.com/jart/cosmopolitan/blob/master/libc/calls/... That's the simplest possible example of a driver with spin locks which uses the x86 IN/OUT instructions.

If you want to take a dive off the deep end right now with Cosmopolitan on metal -- simulated -- then try the following build commands on your Linux terminal:

    git clone https://github.com/jart/cosmopolitan
    cd cosmopolitan
    make -j8 o//examples/hello2.com
    qemu-system-x86_64 -m 16 -nographic -fda o//examples/hello2.com
    sed -i -e 's/USE_SYMBOL_HACK 0/USE_SYMBOL_HACK 1/' ape/ape.S
    make -j8 o//examples/hello2.com o//tool/build/blinkenlights.com
    o//tool/build/blinkenlights.com -rt o//examples/hello2.com