The boot menu and the setup options seem limited in that you can only tell the system to boot from the "onboard sata drive", but you cannot specify which sata drive has priority (other than by its physical connection). I wonder if I'm overlooking a setting here.
Jump forward a decade. I'm referring to the F12 boot menu, which is separate from the BIOS setup. In most Boot menu's all drives are listed, or in this case only the "onboard Sata drive". Okay, well, in this PC there are 4 sata connections. In most system that I've seen any of them could be booted, or at least configured to be the one that is booted when "onboard sata drive" is selected. But not so in this PC, at least not to where I can see it.
The F12 menu isn't separate its part of the bios and only works in CSM Legacy mode.(UEFI GPT partitions are not available to choose which(Physical) drive to boot from either.
The Bios F2 or F12 menus are not a way to multi boot installs from specific SATA ports.
This has never been an option to SPECIFY the port to boot from having multiple OS drives.