On Wed, 16 Oct 2002, Fred Cisin (XenoSoft) wrote:
> > > It has some good information, some errors, and some good and bad guesses
> > > (such as saying that it is probably possible to read hard sectored disks
> > > with PC hardware)
>
> On Wed, 16 Oct 2002, Patrick Finnegan wrote:
> > If you're refering to 'fixed format devices', they seem to be referring to
> > OS device nodes - such as "/dev/fd0h360", not physical (hard-sectored)
> > devices/disks.
>
> NO. For example,
> In "Interesting Formats", (as quoted in the next paragraph) they seem to
> be implying that the original PC diskettes are FM (not MFM), which is
> FALSE.
> Then they list "CP/M, Apple II, TRS-80, etc."
> Then they explicitly mention hard sectored, with the wrong guess that they
> would be readable on standard FDCs.
> Then they say that the 160K/180K formats were double sided; which is
> WRONG.
Ahh, I must have skipped over that part of it. You and I know that
they're wrong, that's good enough, right? Maybe if I get some free time
I'll submit a list of problems to the creator of that doc.
> There are numerous such errors on that page, although overall the content
> is good.
I was only paying attention to the parts that showed how to use the
commands, I wasn't really paying attention to it in that much detail, I
guess.
> > To me, it looks like the hardest part will be attempting to determine what
> > format the disk is in, automatically. Any ideas? My best guess is to do
> > a guess-and-check method, of course this would be tough to verify every
> > possibility, such as varied sector sizes (although it would be possible).
> > I'm guessing that I'll have to use a raw floppy ioctl to make that work.
>
> Fully automatic determination is NOT possible. But you CAN eliminate most
> other possibilities, and reduce it to something that can probably handle
> all of the different formats that you have. SOME parameters, such as
Granted. I was just speaking of the type of 'automatic determination'
that Teledisk does - my primary goal would be to create a replacement for
Teledisk that runs on linux (and *BSD, eventually).
> sector sequence (aka interleave) are trivial to determine manually, but
> hell to do automatically. Likewise, but actually a little easier, "which
> track has the DIRectory?"
I'm not trying to make a miracle data-transfer agent like XenoCopy (I mean
that as a complement), just something to let me make images to transfer
over a network or store as files on a hard drive somewhere.
> If you are willing to program the FDC directly, you can try to read the
> sector headers.
> If you are NOT willing to go down to that level, then:
> 1) try to read, oh say, 512 byte sector #1 Track #4, from track 4, side A,
<snip>
> 2) Once you know the bytes per sector, and sectors per track, then try
> reading from side B. Since side A and side B are normally the same
<snip>
> 3) confirm the maximum track (usually 40 and 80, but sometimes 35 and 77!
> 4) once you have determined the physical format, you can duplicate disks,
> but not retrieve data from them in a reliable way until you determine the
> logical parameters:
<snip>
That's similar to what I was thinking about, but probably a better way of
doing it (I'm lacking a few years of experience.....). As I said earlier,
I don't want to even think about writing a data conversion program right
now..
> BUT, ...
> whatever you do, somebody can screw it up! For example, some formats use
> 8 sectors per track, but FORMAT 9!
> Sometimes somebody takes a previously used DS disk, and reformats, and
> uses a SS format on it. The extraneous stuff on side B can completely
> confuse an automatic selection algorithm.
I think I'm the somebody that you're talking about. If I had a bulk
eraser lying around, that'd probably be helpful.
> I estimate that there are about 2500 mutually incompatible floppy disk
> formats. I've analyzed about a quarter of them, and implemented about 2/3
> of those.
Thanks for the help, I'm thinking I'll try to just play around with a
manual selection of disk format (chose from a list or enter the parameters
manually) for now. I'd just like to get something to play with first.
And of course, it'd be nice to have something that'll convert/read
teledisk format files, so I don't have any reason to worry about having to
use this DOS box sitting next to be to write out disks anymore.
Pat
--
"This fucking university has shown time and time again that it is
completely fucking incompetent when it comes to employing technology"
-- Anonymous
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Received on Wed Oct 16 2002 - 20:02:01 BST
