Lets say that we have two hard disks plugged on Pegasos. Formatted and with MorphOS installed into both. First gots the 2.1 and second got the 1.4.5. How shall we drive the OF to boot from the second HD using boot command?

For example if I want to boot from the second partition of the first hard disk I would type:

Boot hd:1 boot.img

What hard disk name should I use in the boot command to tell the OF to load boot.img from the second HD?

Thanks in advance.

Boot from second hard disk:

// second hard disk, first partition
boot hd0:0 boot.img

// or full path
boot /pci/ide/disk@1,1:0

You can see using this command, what are full paths for devices on your setup:
ls /pci/ide

For me:
cdrom@0,0
cdrom@0,1
disk@1,0
disk@1,1

It depends on how devices are connected (channel, master/slave).

I hope it will help you.