My knowledge is based on the rPi1, but cursory investigation suggests that this is also true on the rPi2:<p>There are several blobs that are necessary to be on the sd-card for boot: bootcode.bin, fixup.dat, and start.elf.  Any bootable sd-card image for the Pi has them.<p>What&#x27;s kind of interesting is that most of what start.elf is is actually an entire OS (ThreadX, I believe), that is running on the VC4 GPU in parallel to the OS on the ARM CPU; and that most of the Linux GPU drivers for it are just shims that send messages saying &quot;hey, ThreadX, would you mind doing this for me?&quot;