Lilo, and grub are linux boot loaders, Windows installs something, and MemTest86 is something that can be booted from a floppy without an OS layer. These are all things the cpu can run without an OS.
how would I go about building uPy to be run "like that" on an x86
I am hoping someone has already figured this out, or has some pointers.
Otherwise I'm off to look at the source and build process for memtest and ipxe