Found a somewhat readable (for a non-programmer) account of how to
load and run "bare metal" programs on a Pi4. It's at:
https://isometimes.github.io/rpi4-osdev/

The author still uses u-boot to load and run his code, leaving the question
of how much code he _didn't_ write remains resident and active.

I'm getting the impression that u-boot starts a considerable amount of
activity on the GPU. Does it simply go away once an introduced kernel is
started? Later on in the tutorial it's clear that bluetooth requires
its own software, which doesn't appear to be open source.

So, just how "bare" is bare metal on the Pi?

Thanks for reading,

bob prohaska

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