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Seagate MFM drive model numbers and differences ?

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    I found the following interesting explanation of "PR" model code in the ST11R/ST11M manual:

    Paired Program drives are shipped with a Seagate controller. They
    are recognized by a "PR" label on the drive top cover. Paired
    drives are shipped formatted with a small DOS partition
    containing the installation program, INSTALLR, which will low-
    level format and partition your drive. You must supply the DOS
    program. The ST11M/ST11R can recognize whether a drive has the
    Paired Program software loaded, or has been previously installed.

    Paired Program drives with formatted capacities greater than 32
    MBytes have Disk Manager partitioning software loaded. This
    utility has been customized by Ontrack for Seagate. Refer to
    Section 2.1 for special instructions on formatting Paired Program


      One wonders about the "pairing". Might it be to automatically deal with known bad tracks? Most MFM controllers can easily reformat and partition disk drives. I guess for some people it is kind of intimidating. Getting such things already done and only requiring the OS install might be as much as the average person expected to deal with. Also, for people that will build 10 or more system a day for businesses, it might make sense. In such an environment, time is not free. Something I might fiddle with for a few hours is not something that makes sense in an IT environment. Getting it done quicker might make sense, even for someone that knows what they are doing.


        Originally posted by chris_nh View Post
        I've also seen some part numbers like "ST-251 -1". Same curiosity... what does -1 specify?
        The ST-251-1 drivers were an improved variant of the standard 251 drives with faster transfer speeds and seek times. At least according to the Red Hill Guide.


          Originally posted by AndyM1981 View Post
          The ST-251-1 drivers were an improved variant of the standard 251 drives with faster transfer speeds and seek times. At least according to the Red Hill Guide.

          Transfer speed is the same, just the seek times are improved.



            I am not sure what you are specifically looking for. However, if you look at here:


            you will find documentation for all seagate drives, incl. their specs. This might help you find out the differences you are looking for.

            Best Regards



              So I found an interesting thing to add to this thread about the "PR" or "Paired Program" drives ... I actually came across a factory print out for a paired ST-250R drive. This appears to be the piece of paper that was printed and shipped with the drive. The print is faded so a photo will be hard, but the information is interesting enough that I'll type it out below. It does give some insight into what the factory was doing with the PR drives. They came with a pre-installed installer program and controller card, which is a great attempt at making MFM/RLL more friendly for end users. Nothing special about the controller, just that it was guaranteed to work with the drive and the installation software would help the customer through formatting.

              Anyway, check it out below.. here is the info on the drive print out sheet from ST-250R PR drive


              ST11R MATE PROCESS ver 3.03

              ST250R MATE SOFTWARE: ver 1.03

              INSTALL SOFTWARE: ver 3.0
              ONTRACK SOFTWARE: ver 3.50

              START: Sat Dec 16 23:11:54 1989

              23:11:55.09 Resetting controller
              23:11:55.31 Formatting reserved cylinder (-1)
              23:11:55.80 Downloading drive geometry
              23:11:56.02 Verifying drive geometry
              23:11:56.24 Downloading Manufactures defect map
              23:11:56.57 Resetting controller
              23:11:56.62 Formatting 16 data cylinders
              23:12:05.14 Downloading installation software
              23:12:24.80 Verifying installation software
              23:12:44.68 Resetting controller
              23:12:45.78 Parking drive

              Drive Geometry
              Drive type : ST250R
              Serial number : 25572852
              Cylinders : 667
              Heads : 4
              Sectors/track : 31
              Interleave : 4
              Onboard software flag : TRUE


              There is also a 1 track defect llist and a "PASS" printed large at the bottom. Pretty awesome stuff, so apparently there is a flag for onboard software in the reserved cylinder that the ST11R controller will recognize, and maybe do something like launch the software at boot??

              Plenty to explore here. Anyone ever seen this software before? It would be a rare find, but a "new old-stock" PR drive might have it. I picked this one up, but it is a non-working unit unfortunately.


                Also, here is a little more insight into the software function:


                  So, today I received an ST251-1 with no known low level format, but when connected to a ST11M controller, it does indeed appear that the ST11M/R controller BIOS is checking for the Ontrack software at boot!

                  The existing low level format on this drive is not recognized by ST11M or WD1002 or Everex controllers. This particular drive actually has an Everex sticker on it, so I assume it was originally packaged with an Everex controller. Sometimes trying these old drives on different controllers will work, but this drive otherwise appears ready for a fresh low level format. The bearings are very loud in this one, but the drive works and passes seek tests in Speedstor.

                  I'm going to explore this a little bit, but it seems like an interesting boot behavior built into the ST11M/R BIOS and I wanted to share it.