that's getting complicated.

I am thinking about including a usercode-module (Assambler, max, 64k) to my BIOS. This usercode-module gets loaded in the last POST (Jump) of my BIOS. --> So far, it is possible. No need to jump back to BIOS.

But this usercode has to be able to load a kernel or another loader on an usb-device. Important is, that the usb-device does not need an boot-sector (it is not bootable). It is simply a FAT filesystem.

For example the GRUB-Loader:

Stage1 and Stage1.5 of the grub loader has to be implemented in the usercode. Stage2 is a file on the usb-stick.

Is this possible? I belive a huge problem will be to implement a usb-driver in usercode...

Waht is the best starting point? (GRUB?)

Thanks für every thought on this.