🚀 go-pugleaf

We are running a number  of 6150 model 125's which we are upgrading
to AIX  2.2. In the process of doing this, I found that the VRM program
and Diagnostics boot disks would not boot  (but the install and maintenance
one would) on some of the machines. 

As this has happened before, I called the engineer who said he would change 
the system board. (This has sucessfully fixed the problem in the past 
although he didn't know why.) 

When he went to order the board from the  stores they told him that the
problem is that the default boot device (stored in batery backed RAM)
has been changed from floppy disk to hard disk. The reason that install 
and maintenance worked was that even with the boot device changed from
floppy, it always checks, just in case it is the install diskette and boots
from it if it is.

In order to change the boot device back to floppy, he suggested using
either ctrl alt A when the floppy drive was accessed at boot time 
or disconnecting the battery to the RAM for twenty minutes. 

The former didn't fix the problem but the latter did.

Can anyone tell me :
a) Why would one want to change the boot device in this way ?
b) How and why has it been changed ?
c) Having changed it, is there a better way to reset it ?

Thank you.