43p 120

I have acquired a 43p 120 (7248-120) and I have two questions:

Can anyone remember what is the highest version of AIX which I can install (5.1 I believe)

and

Can anyone remember how to boot this from the CDROM (boot floppy?)

One point to add is I have attached an IDE CDROM and selected this in the SMS menu as the only bootable device but it will not boot. There is a second CDROM drive in the machine but this is SCSI and not in the boot from list in SMS.