SX machines booted from a floppy unless like this machine a hard drive has been added.
The original motherboards could not detect the hard drive parameters. These machines came out in 1992. Nor could they determine the type of floppy (it has to be set manually like other CMOS settings) This is why Bridgeport put a sticker on the hard drive (if purchased from them) of what the hard drive parameters were. With some of these old machines, I have had to put the hard drive into a PC test bed I have to determine the hard drive parameters. I also use this test bed to test BMDCs with the B3T test, FDISK & FORMAT & load hard drives, test ISA video and I/O boards, and make new floppy disks.
Another trick is to remove the I?O board and clean the edge connector with a soft eraser. This has brought back to life many machines.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)