Wow. I didn't know that anybody besides Commodore ever used XT IDE. I

a couple of WD-98???-X drives, one in a Commodore Colt that I use for ROM burning. IIRC, WD made 20Mb and 40Mb XT IDE before moving on to AT IDE. Commodore even designed-in an XT-IDE port on their A2091 and A590 disk controllers for the A2000 and A500, respectively. The A590 did ship with 20Mb XT drives; the A2091 did not have the 40 pin connector soldered in

It does work; I have retrofitted one. They are slow. And, yes, the ST251/251-1 are both MFM. I use them on ancient DEC

-ethan