HD floppies on a ZX Spectrum

This might be a silly question... Since the specs of the MGT +D disk interface are now out there in the public domain... http://www.worldofspectrum.org/NotThePlusD/ ... but 720kB 3?" floppy drives are getting rather scarce, I was wondering... would it be viable to build a version that supported 1.4MB "HD" drives? I realise this would mean a different FDC chip, but are there other implications apart from tweaking the DOS? I know few 8-bits supported HD disks, but I don't really understand why. My electronics knowledge is poor. (Cue Tony Duell.) I am guessing that an 8-bit would struggled to read/write data fast enough to keep an HD diskette controller supplied with data, but I was wondering if that could be overcome with interlacing or adding some cache RAM? This is probably a completely pointless exercise - people seem more interested in using CF or SD media these days, but I enjoy the nostalgic element of actual floppy diskettes. -- Liam Proven ? Profile: http://lproven.livejournal.com/profile Email: lproven at cix.co.uk ? GMail/G+/Twitter/Flickr/Facebook: lproven MSN: lproven at hotmail.com ? Skype/AIM/Yahoo/LinkedIn: liamproven Tel: +44 20-8685-0498 ? Cell: +44 7939-087884