Floppy-Universaladapter gesucht

Q14: Can I read my 8" disks with my PC?

A: (John Baker, Tom Sullivan)

   With a program called 22disk, and an adaptor board that you can
   make, you can read those disks on your PC. All it takes is
   rearranging some of the lines on the 34 pin cable, and wiring them
   to the 50 pin cable, and you're in business.

   The interface on 8" drives and 5 1/4" drives are essentially the
   same.  The 34 lines on a typical 5 1/4" controller are sufficient to
   control most 8" disk drives using soft-sectored disks.  Here, is a
   diagram for a basic conversion cable to allow connection of an 8"
   drive to an IBM-compatible, AT-style (high density) controller.

                                                      8" disk drive
   PC-AT style controller                       Based on Shugart SA-851

   Grnd. Sig.  Sig. Name                             Sig Name  Sig Grnd
     1     2   Double/High Density ->>
                                    >>- Write Current Switch/    2    1
                                   Active Read Compensation
                                   User Customizable I/O pins    4    3
                                    "         "       "    "     6    5
    33    34 **Ready ---------------<<------------ True Ready    8    7
                                    <<-------------#Two Sided   10    9
    33    34 **Disk Change ---------<<----------- Disk Change   12   11
    31    32   Side 1 Select ------->>-----------#Side Select   14   13
     3     4   In Use/Open --------->>---------------- In Use   16   15
    15    16  *Motor On ------------>>------------- Head Load   18   17
     7     8   Index ---------------<<----------------- Index   20   19
    33    34 **Ready ---------------<<----------------- Ready   22   21
                                    <<---------------##Sector   24   23
     9    10   Drive Select 0 ------>>-------- Drive Select 1   26   25
    11    12   Drive Select 1 ------>>-------- Drive Select 2   28   27
    13    14   Drive Select 2 ------>>-------- Drive Select 3   30   29
     5     6   Drive Select 3 ------>>-------- Drive Select 4   32   31
    17    18   Direction Select ---->>------ Direction Select   34   33
    19    20   Step ---------------->>------------------ Step   36   35
    21    22   Write Data ---------->>------------ Write Data   38   37
    23    24   Write Gate ---------->>------------ Write Gate   40   39
    25    26   Track 00 ------------<<-------------- Track 00   42   41
    27    28   Write Protect -------<<--------- Write Protect   44   43
    29    30   Read Data -----------<<------------- Read Data   46   45
                                    <<------##Separation Data   48   47
                                    <<-----##Separation Clock   50   49

   This diagram also works in the other direction--that is, to attach
   high-density 5 1/4" drives to an 8" controller.

   Notes:

   * - It seems to be a logical substitution since the vast majority of
       8" drives have continuously running spindles and instead of
       MOTOR ON require a HEAD LOAD signal.  Also, a controller sends
       MOTOR ON before a DRIVE SELECT.

   **- Most 5 1/4" disk drives do not provide a READY signal but send a
       DISK CHANGE signal on line 34 of the interface.  An 8" drive has
       provisions for both signals.  Likewise, most AT-style
       controllers expect a DISK CHANGE signal on line 34, so lines 33
       and 34 should be connected to lines 11 and 12 of the 8" disk
       connector.  Also, some 8" drives provide a TRUE_READY signal
       which is more useful than the standard READY.

   # - Unused on single sided drives (SA-800/801).

   ##- Used only on hard-sector configured drives (SA-801/851).

   Some 5 1/4" disk drives have the option of providing _either_ DISK
   CHANGE _or_ READY on line 34 (in particular, the TEAC FD55R
   series).  Some 8" disk controllers do not care about the DISK CHANGE
   signal, but must have the READY signal.  If you are attaching a
   high-density 5 1/4" drive to an 8" controller, you may get away with
   making the drive always ready by shorting lines 21 and 22, but this
   may cause a few re-tries when switching sides.  If your drive offers
   a READY signal that your controller can deal with, by all means use
   it.

   The MOTOR ON/HEADLOAD dilemma may also have an alternate solution if
   you are connecting 5 1/4" drives to an 8" controller.  Some 5 1/4"
   drives permit motor turn-on by means other than the MOTOR ON
   signal.  For example, the TEAC FD55R series of drives may be
   configured to turn the motor on based on the state of the IN USE
   light.  The IN USE light can, in turn, be set to turn on only on
   drive select.  Thus selecting the drive automatically turns on the
   motor and neither a MOTOR ON or IN USE signal need be present.

   Another way to handle 8 inch drives on a PC is with a Microsolutions
   Compaticard IV, if you can find one. (MicroSolutions no longer
   offers this product.) It has the necessary software support to
   properly handle 8 inch drives, and in both SSSD and DSDD.  This
   controller can be set up as both a primary controller, or as a
   secondary. It can support 4 drives, of any type, including 2.8 meg.
   It supports two MSDOS 8 inch formats, SSSD (about 250k) and DSDD
   (1.2 meg). It works perfectly with 22disk, and can read and write
   almost any 8 inch CP/M format.

Q16: Can I use the newer floppy drives on my old machine?

A: (Jeffery Jonas, Axel Berger, Dave Wilson)

   You can. 3.5" and 5.25" are fully hardware compatible and your
   computer will never notice the difference - unless the 5.25 are HD
   drives. As 3.5" drives are able to step faster and draw less
   current, this direction of swapping is totally uncritical. The other
   way round sometimes proves more tricky.

   Both 3.5" and 5.25" drives have the same 34 pin interface.  3.5"
   disks spin at 300 RPM thus the 250k/500k data rates.  5.25" disks
   spin at 300 RPM for all but the 1.2 Meg capacity, which is 360 RPM,
   thus the ratios:

        15 sectors per track / 18 sectors per track
                   = 300 RPM / 360 RPM
                   = 1.2 meg / 1.44 Meg

   All 8" floppy disks spin at 360 RPM too.


   Most old systems didn't use pin 2, 34.  That's GOOD NEWS since
   modern 3.5" floppy drives place signals there that the old
   controllers can't handle.  The ready/disk changed lines changed from
   the "XT" generation drives to the "AT" generation drives.  Older
   floppy drives had jumpers for drive select 0-3 and where to place
   the status signals The "AT" floppy drives assume the "AT" signals
   and usually allow only setting the middle 2 drive selects, thus the
   cable twist nonsense.  for completeness, here are the pinouts:

        Mini/Micro Floppy Interface

        Pin#  Description         Alternate Functions
        ----  -----------         -------------------
        1     GND                 Eject, Disk Change Reset
        3-33  Odd pins are GND
        2     High Density
        4     Head Load           In Use, Eject
        6     Drive Select 3
        8     Index Pulse +
        10    Drive Select 0      Motor On A    \  IBM twisted
        12    Drive Select 1      Drive Select B \ cable - both
        14    Drive Select 2      Drive Select A / drives are
        16    Motor On            Motor On B    /  strapped DS1
        18    Direction
        20    Step
        22    Write Data
        24    Write Enable
        26    Track Zero +
        28    Write Protect +
        30    Read Data +
        32    Select Head
        34    Disk Changed +      Ready +

              + signal from drive to controller

  The following table is extracted from the CompatiCard manual:

           Card        34   37              50   8 Inch Drive
     Signal Name       Pin  Pin  Direction  Pin  Signal Name
     ============================================================
     Programmable      2    3       --->    2    Low Current
     Index             8    6       <---    20   Index
     Drive Select 1/3  12   8       --->    28   Drive Select 2
     Motor Enable 1/3  16   10      --->    18   Head Load
     Step Direction    18   11      --->    34   Direction Select
     Step Pulse        20   12      --->    36   Step
     Write Data        22   13      --->    38   Write Data
     Write Enable      24   14      --->    40   Write Gate
     Track 0           26   15      <---    42   Track 0
     Write Protect     28   16      <---    44   Write Protect
     Read Data         30   17      <---    46   Read Data
     Select Head 1     32   18      --->    14   Side Select

   The odd pins of 34 pin connector to odds of 50 pin connector.
   Pins 21/37 of the DB-37 go to the odd pins on 50 pin connector.