From NetBSD:

From NetBSD:
Startup modified to work with kernel loaded directly into fast memory.
This removes the need to have enough chip memory to load the kernel
when booting.  Kernel memory is dual-mapped (VA == 0 and VA == PA)
for enabling the MMU, and the VA == PA mapping removed after start_c()
has completed.  Chip memory is still required for the /dev/reload
process.