The first hard drive interface in the PC compatible world came with the IBM PC/XT. The XT included a "fixed disk drive" controller designed by Xebec. The controller used an interface called the ST-506 after Seagate ST-506 hard drive. The ST-506 was a 5MB drive and used a two-cable interface. The IBM original controller only officially supported one type of hard drive in its first two iterations, the ST-412. The ST-412 functioned like the ST-506 but had a 10MB capacity.
Later, Seagate released the ST-225, a 20MB hard drive that could be found in late model XTs and perhaps the IBM PC XT/286. IBM released a final revision of its fixed disk controller to support this drive.
MFM drives can take up a full-height 5.25" drive bay. These bays are seldom found outside the original IBM PC, XT and XT/286. The ST-412 is a full-height drive, the ST-225 is a half-height drive.