Two of my many home computers use older motherboards from Giga-byte. One is a P35-DS3R and another an EP35-DS4 . Both are based on the 2007-vintage Intel P35 chipset.
As I'm constantly shuffling disks, operating systems, and messing with various things, I often find myself unable to boot. Multiple operating systems on the same machine often have a way of messing with each other. Such is life.
For years, I have been using a very useful tool called DFSee to recover from such dreadful situations . I'm normally booting this tool from a CD-R . DFSee first boots to FreeDOS . On the two aforementioned motherboards, if the optical drive is connected to one of the SATA ports on the Intel controller, the boot process inexplicably hangs after word "FreeDOS" is displayed. This is very problematic. I have the latest - and last - BIOS release for these motherboards, so a fix will not be forthcoming from the manufacturer. There is a solution for this, however : disconnect the optical drive from the Intel SATA controller, and plug it into the Gigabyte JMicron-based 2-port SATA controller. FreeDOS will then successfully boot.
I'm not sure if this problem still exists on more recent Intel-based Gigabyte motherboards. I have two other more recent Gigabyte motherboards, which are AMD-based, and DFSee and FreeDOS boot fine regardless of which SATA controller the optical drives are connected to.