21 May
2013
21 May
'13
11:48 a.m.
On 05/21/2013 10:26 AM, Liam Proven wrote:
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.
With a 4MHz Z80 CPU, it's possible. There was a stepping of the WD1772
that could be goosed to do 500KHz data rates (The 1770 and 1772 are
denoted by WD as "minifloppy controllers"). You'd have to change some
time-critical components, such as the FDC crystal and probably rewrite
the floppy routines to accommodate a different format, but it's all doable.
I think the Atari ST people goofed around with this one some years back.
--Chuck