MFM/RLL data recovery

[Tom Peters]

At 04:21 PM 4/4/2005 -0500, you wrote:
>The drives in question are a ST-225 20MB (615/4/17) that came out of an
>XT (so would have been using a 8-bit controller) and a ST-238R 30MB
>(615/4/26) of unknown origin.

Need RLL controller for the ST-238 and MFM for the ST-225. Sorry if that 
was already abundantly obvious.

>I don't have or even know what the original controllers were, the
>machines were gutted/given away years ago by the owners.
>
>I have a 386 testbed which I'm using, and plan to laplink the files over
>to another machine once they are accessible.
>
>The only card in the 386 is a VGA card.  Turbo is off.
>
>I have the following controllers:
>- WD1002A-27X 8-bit RLL
>- Adaptec ACB-2370A S2 16-bit RLL/floppy
>- WD1002SV-SR2 16-bit RLL/floppy
>- Everex EV-346 16-bit MFM/floppy

I have docs for the WD cards. The 27X sounds (without looking) like an RLL 
controller.

>I also have two Miniscribe 8438 30MB RLL drives.  However, they were
>used with the 27X, which means the geometry is ambiguous depending on
>how the jumpers were set when it was formatted.
>
>Now, I'm either doing something wrong or all these drives are dead.
>
>I am using a floppy cable with a twist in it and a 20-pin data cable.

That certainly will NOT work. The floppy cable is for floppy drives. Get a 
MFM data cable.

>All of the drives spin up (the Miniscribes needed a little coaxing) and
>sound "healthy" as they dance their little self-test jigs.  Here's where
>the trouble starts.


>I tried the ST-238R with all three of the RLL controllers.  With the 27X
>and with no hard drive entered in the NVRAM setup, since the BIOS can't
>be disabled, it runs the BIOS, which can't figure out what's going on
>and returns a 1701 POST code.
>
>With both of the 16-bit RLL controllers, 615/4/26 entered in the NVRAM
>and the controller BIOS disabled, the drive makes a repetitive seeking
>sound like an ECC retry about twice a second, until eventually the BIOS
>gives up and returns Drive C: failure.  What this seems to indicate to
>me is that the drive was formatted with different geometry, or the
>tracks have drifted so bad it can't get its bearings.
>
>I also tried the Miniscribe drives with the 27X for kicks.  Everything
>sounds normal, including the long growl that I remember that
>drive/controller combo doing during POST.  But, a 1701 is returned,
>which isn't normal - this drive *used* to work with this exact
>controller.

Wrong 34-pin cable. Also check the markings on the controllers and the 
drives very carefully for the pin 1 identification. Perhaps all the solder 
pads are round, except for one which is deliberately square, (that's pin 1) 
or maybe it's silk screened on the board/drive.

>The only MFM controller I have is the Everex, so I tried the ST-225 with
>that one, entering 615/4/17 in the NVRAM and disabling its BIOS.
>Unfortunately, I get mostly the same behavior as with the ST-238R;
>except that with this drive, the retry clicks are about a second or two
>apart.  Eventually the BIOS gives up anyway.
>
>I'm fresh out of ideas at this point.  Maybe I have a bad cable?  Do I
>need to find the exact controller the drives were paired with - what
>were the most common ones for each drive?  Is the 386 the problem, too
>fast for these cards?

No, it's not too fast. Try the right cable and the Western Digital 
controllers.



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