They were garbage that happened to be 0 in many cases. (real_to_prot()
happens to leave the value of the real-mode %cr0 in %eax and the
memory-size BIOS calls usually don't touch the upper bits of %eax.
The upper 16 bits of %cr0 are usually 0 at boot time, at least on
486's.
Should be in 2.2.
07addd421e