Making multiple bootable partitions on diskonchip

I have a 72MB Diskonchip which I have partitioned into two parts
partition 1 : QNX : 36 MB type 77 marked bootable
partition 2 : QNY : 36 MB type 78.

Both of them contain the compelete QNX OS . The multiple partitions are for
redundancy for an experiment. So in case one fails I need to able to boot
from other one automatically.
Currently, I am able to boot from only one of them ie partition 1.
Can someone please help me on this?