8 Dec
2010
8 Dec
'10
11:52 a.m.
On 7 Dec 2010 at 19:50, Tony Duell wrote:
Does that floppy emulator work on _any_ possible floppy controller, or
does it assume a 'normal' FM or MFM one (or perhaps an Apple ][ GCR one)?
There are some pretty strange ST412 controllers out there -- take a look
at the PERQ one, for example. It does not uise normal sector headers. And
of course that's one machine that it would be useful to have a drive
emulator for.
-tony
I wonder if you could do somethjing akin to the
DiskFerret and simply
record the transistions (sampled suitable fast) of the write data
signal and replay those samples when readoing. OK, it would be
wasteful of the flash memory space, but as many ST412 hard drives were
around 20MBytes, but modern flash memory cards are a few Gbytes, I
don't think that would be a major problem
Speaking as one who has studied the problem a bit and who has no
intention of implementing anything, I think that a sampled stream is
overkill.
While it's true that the result is something that's controller- and
format-independent, it's more straightforward and requires less
horsepower to simply generate the formatting information, inserting
the data as required. There's a floppy emulator that does this with
comparatively little RAM and runs on an 8-bit 8MHz AVR. One also
doesn't need to worry about aliasing effects.