http://osfree.i2p/forum/viewtopic.php?p=399
I.e., the loader loads a multiboot kernel, which can be a Linux kernel or kickstart for L4 microkernel. For custom kinds of kernels, like OS/2 kernel, a special multiboot kernel can be created. It relocates itself to the address within 1st megabyte (conventional memory), switches back to the real mode and starts IBM's os2ldr, which, in turn, starts OS/2 kernel.