In IDE, we use the jumper settings to distinguish Primary or Secondary Master and Slave Drives
But in SATA, there is no jumper setting. If we connect two SATA HDDs simultaneously to the motherboard, with each having its own OPERATING SYSTEM installed in it, then which one of the OS would boot. as we know that there can be only one MBR.
I found the option of choosing the SATA HDDs for booting in ASUS Motherboards by pressing the F8 key during startup
How can we choose this option in the other motherboards ?
The first drive you installed windows on will hold the mbr. If you then install windows on the second drive it will edit the mbr so both oses will show up at boot. Now if you installed windows on each drive when they were installed by themselves you will have problems.
If two SATA hdd's are installed, both containing a bootable OS, one of two things will happen, depending on motherboard manufacturer:
One OS over the other will boot or the system just won't boot (older machines).
By the way, there is 1 MBR per hard disk, so there would be two, and the BIOS either boot one over the other or gives up, throwing it's hands in the air.
You may be able to disable the bootable status one of the disks and this would solve the problem. If your BIOS does not support that, you cna use a partition managing tool like the GParted LiveCD to make one of the disk's primary partition non-bootable. This will prevent the BIOS from trying to boot the disk whether or not the BIOS explicitly supports it by lowering the valid MBR's to just one.
If you wish to boot between the two, you'll have to either install a boot manager or editing the C:boot.ini to support the second disk.
To "choose the boot options" like F8 on your board, it varies from manufacturer to manufacturer, my old moard used "Del", my current one uses F2, my laptop uses SHFT+F1. You have to either check out the manual or read it from the screen as it boots up (usually at the bottom of the screen during initial boot).