Sorry - this was actually a hypothetical question I guess. We are
running 7026-B80s and I refer specifically to system and service
processor firmware.


I am just curious - in the event of a problem incurred by the new
firmware level - how should one go about "backing out" of the update/


The procedure is discussed in detail for each firmware level you might
download. This includes how to handle the diskettes, or your previous
XXXXX.img files should a restore be necessary.

There is normally an apply/restore section for:
command line method
Update Flash Diagnostic Service Aid method
Service Processor Menu method

I have never had a firmware or service processor firmware
failure/corruption during my 9+ years with AIX. The failures I have
heard about normally resulted from a lack of patience.

On my systems checkpoints 99FF and 99FD alternately appear while the
update occurs. Be PATIENT... and you should be ok