Epson EQUITY 386SX/16 PLUS - Manual (Page 186)

8. Both the diskette drive and hard disk drive sockets are
located on the main system board on the left side of the
subassembly, as shown below.
diskette
drive socket
hard disk
drive socket
subassembly
Both sockets have a notch on one side. The hard disk
drive socket is a bit longer than the diskette drive socket.
B - 5 2
Installing and Removing Disk Drives