Which Macs have the floppy disk controller on a
separate/replaceable
board?
Well, actually, any Mac with expansion slots can take an FDC card. I have
one of the Apple manuals on designing peripheral cards for macs, and the
example is an MFM-compatible floppy controller (!).
Apart from that, what's the problem with soldering on the mainboard? Some
of us do it all the time. And don't most modern PCs have the disk
controller on the motherboard now? I've certainly seen PC motherboards
with a 34 pin header for the floppy drives.
-tony