I'll also add the Jonathan (Glitch) has taken over the "what
motherboards can do what with floppies" list.
Interestingly, a lot of later legacy-floppy equipped motherboards do
very well with regards to supporting FM reading/writing--yes, even P4,
AM3+ and other boards. (N.B., I said "later" not "recent" or
"bleeding
edge").
Much to my surprise, a P3 Intel i820 (that's the one with RDRAM) FIC
board not only handles FM, but 128-byte sector MFM.
P1 and 486 boards with integrated floppy controllers tend to be very
spotty on anything but MFM support.
Check glitch's table--there's an "fdtest" utility that will tell you
what your FDC can do--or not.
--Chuck