19 Jun
2010
19 Jun
'10
1:22 p.m.
On 19/06/10 20:59, Chuck Guzis wrote:
The "MFM test"? As in, "are there two '1' bits directly following
each
other in the encoded data stream?"
But it's true that histograms are good for figuring out which disc
formats are likely to have been used... and the math behind the method
is solid.
Chuck is very
fond of histograms.
If it doesn't pass the MFM test, that's the first place I go. 2
peaks=probably FM, 3 peaks = probably MFM, 4 peaks = probably MMFM.
5 peaks = maybe GCR. On occasion, I have to build something to handle a
peculiar setup.
Catweasels aren't the end-all, nor are any others. For example, try
putting a Catweasel on a 2.8" DataDisk drive.
Are those similar to the Mitsumi Quickdisk (nee Famicom Disk System)
discs? Basically a continuous stream of binary data, a SEEK_TO_START
input and a HEAD_AT_START status output?
I'm surprised that no one's showed up with
some floppies from a
Memorex 651 drive yet.
That looks fairly standard, at least in terms of the I/O interface
(looks like a Shugart variant to me).
32-sector, soft-sectored, 64 tracks. So probably not a standard track
pitch then... you're probably pretty screwed if you don't have a 651
sitting on a shelf.
Although if you were really determined you might be able to "creatively
misalign" an 80-track drive to read the data, but you'd have to fudge
the alignment for each track...
It's great fun if you're the sort of person
who can look at a problem
and have the patience to wait for an "ah hah!" moment rather than
trying to beat it to death. If you're the "gotta solve it now" type
of person, you're probably in for a lot of headaches.
I'm the sort of person that likes to know how things work. Once I've got
an "interesting project" to play with, I'll follow it to the logical
conclusion.
Kinda like a small-scale version of "solving the {Enigma,Lorenz}
cipher", I guess... :)
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/