The BBC IDE controller replaces the Acorn SCSI controllers and Winchester discs for BBC microcomputers. It can be used with almost any off-the-shelf IDE drive. it uses ADFS (or HADFS) which have been patched to support IDE. The controller is available as a kit or pre-assembled.
Full details, including how to buy, are on J.G.Harston's mdfs.net .
J.G.Harston BBC IDE controller (front)
J.G.Harston BBC IDE controller (back)
The controller connects to the 1MHz bus and only uses 2 ICs (74HCT02 & 74HCT139). All BBC filing systems use 8-bit sectors, so only half the actual drive space is useable without using specialised software.
See mdfs.net .