I've got at least 2 mobos where pressing F-whatzit at the POST allows you to boot from the first, second or whateverit-th physical hard drives.
I stand corrected!
there is another option to select primacy of HDD: HDD1 or HDD2
Yes, I got that wrong - the first PC with 2 IDE disks I looked at is an old Compaq with a 1999 BIOS. No possibility of re-ordering the Boot drive. The next PC I checked has a 2006 BIOS but only had one disk (duh!).
But this PC has a 2001 BIOS and I can enter the BIOS and select which drive will be examined for an active boot partition.
I haven't got one where the boot disk can be selected without configuring the BIOS, but I have no doubt that Mac is correct.
SD