After some test install drbl to Raspberry and found some new idea for multi-arch. Is it possible to build a ARM-DRBL-Server for ARM or X86 client machine, or X86 to ARM client via network boot?
This post show us how to boot filesystem from NFS server.
If you really want to arm pxe boot we can try BeagleBoard xM, OMAP4 Panda or OMAP4 Panda board.
In some ARM board like Raspberry the firmware (and kernel) is on the FAT partition of the SDCard and you must have both to correctly boot the board. In other board like Cubieboard2 you have the internel NAND with the firmware (and the OS) and use u-boot as boot, so you can easly modify it and let the board to start with network OS.