I would boot to OS3.9 partition/hard drive to access the classic stuff, or boot to OS4.0 partition/hard drive for the latest PPC offerings.
Imagine you had both PPC motherboard and A1200... You could run both
classic stuff and OS4 software simultaneously. Not to mention old
hardware is crippling PPC performance on SharkPPC still.
I really mean that and every time you switch OS you must close IRC
sessions etc... I had such dual boot system on my A1200 and it was not
really convenient. Usually I could not switch OS when I wanted to
because someone was leeching from my FTPd or haning on dynAMIte
server.