MFM/RLL data recovery - test-drb@ccmp.vtda.org

4 Apr 2005

Replying to a bundle of posts:

...
  IBM used a twisted cable with their hard disks - in
order to avoid having
 to explain "Drive Select" jumpers to their [Computerland level] dealers.

 The hard drive cable twist is NOT the same twist as for floppies! 
Oops.  See, I saw a mention of a twisted cable in the Miniscribe manual
which came from Hard Drives International, so I thought I was okay
there.

Anyway, I switched to a straight through connection.  I tried the
Miniscribe drives with the 27X and the ST-238R with both the 27X and the
WD1002SV-SR2.  With the 27X I get no POST/BIOS complaints, but the
system tries to go to ROM BASIC, so I guess it is ignoring the connected
drive.  With the WD1002SV with BIOS disabled and 615/4/26 entered, then
I just get Drive C: error from the BIOS.

...
  If you are trying to recover files you are probably
wasting your time, the 
 XT controllers used unique formatting and you will never read the data off 
 of the drives without using controllers indentical with ones used 
 originally.  It is not good enough to use the same brand or even chipset. 
Is that true for MFM drives too?  I know RLL setups were picky about
controller/drive compatibility but I didn't think MFM would be also.

...
  Another problem I had with early MFM hard drives was
they needed to be
 read with the same model of controller that formatted them. 
... I guess so.

...
  For the ST225 look for a DTC 5150 or a western digital
1002-WX1 HD
 controller. These were two of the most common HD controllers for XTs. 
Thanks.  I'll ask the owners if these models ring any bells.

...
  I doubt that you can read them with any of the 16 bit
cards. 
Are drives formatted with 16 bit cards generally compatible with each
other?

...
  When I put away any XT drives that I wanted the data
off I kept the
 cables and controller card with the drive. 
Yup.  I certainly wish that were the case here.

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

...
  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. 
It is actually silk screened on all these boards.  No problems there.

-- 
Ryan Underwood, <nemesis at icequake.net>