MFM/RLL data recovery
cctalk at randy482.com
Tue Apr 5 13:45:12 CDT 2005
From: "Ryan Underwood" <nemesis-lists at icequake.net>
Sent: Tuesday, April 05, 2005 12:55 PM
>> A few times I've seen different PC controllers from the same manufacturer
>> (i.e. WD or whatever) work from one model to another but not be able to
>> without a low-level formatting (booting from a floppy allows access).
> Now *this* is interesting. I was assuming that if the drive was going
> to work at all, it would be bootable too. Why is is that you wouldn't
> be able to boot from the drive, yet you'd be able to read it if you
> booted from some other media?
I have no idea why just something I had run into, as I remember it was
between two WD cards, one 3/4 length vard vs. 1/2 length card.
Sometimes the only answer I had was just because, I never had technical
manuals on the cards and I just used them "blind" accepting that they do
what they do. The problem turned up when I replaced a bad controller, I
tested it back and forth to try and figure out how to make one boot when
formatted from the other but never got it to.
>> Does the controller require a real 8 bit machine, yes not all 8 bit
>> controllers even worked in 16 bit computers.
> Any examples of problem controllers in this area?
I have one around somewher, an Adaptec 8 bit only RLL controller I know DTC
had some 8 bit only I'm sure there are others.
You can test your controllers by using a drive you know is good but you are
not interested in the data and try formatting it and using it with your
controllers (very time consuming since you have to format for each
controller). Doing this will verify that everything minus the hard drive is
>> On IDE all of the truly low level stuff is 100% hidden so the only
>> compatibility problems with IDE tended to be drive geometry (early
>> when the same drive could be addressed by different geometries) .
> Yeah, I had a Fujitsu IDE drive die on me recently. I was able to get
> the data by swapping the drive PCB with that of another drive which was
> the same model, but not identical (6 months newer, different stuff on
> the label). I was surprised that it actually worked.
> Ryan Underwood, <nemesis at icequake.net>
Once people get used to an IDE just plugging in and working we tend to
forget the problems of classic systems hard drives :)
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