Oktagon Reference

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  The Oktagon 2008S is a combination SCSI-2 (but not Fast SCSI-2) and 16-bit
  RAM board, much like the A2091. However, the Oktagon in combination with the
  A4000 does not have the extremely slow transfers of the A2091 (see Slow A2091 Problems
  because the Oktagon does not use DMA; it uses interrupt-driven PIO.

  The Oktagon uses 1Mx4 ZIP chips, either static column or page mode, to
  provide 16-bit RAM. An IDE version of the board is also available (2008AT).

  Oktagon ROM versions of less than 6.5 may have problems with removable
  media devices. The recommended (current) version is 6.8. To see the current
  ROM version number, press F1 during powerup, or use C:Version on
  oktagon.device.

  Problems have been reported using the Oktagon with 68060 accelerator
  boards. The Oktagon ROM uses a MOVEP operation, which is an illegal
  instruction on the 68060. An A4000 with a 68060 board and the Oktagon will
  refuse to boot because of this problem.

  Board Layout
  _________________________________________________________________
 |          Jumper                                                 |___
 | :        ::::::           :: SCSI                               |
 |LED       123456           :: Connector                          |
 |                           ::                                    |#
 | ::::::: 63,83             ::                                    |# External
 | ::::::: 23,43             ::                                    |# SCSI
 | ::::::: 62,82             ::                                    |# Port
 | ::::::: 22,42             ::                                    |# (DB25)
 | ::::::: 61,81             ::                                    |#
 | ::::::: 21,41             ::                                    |
 | ::::::: 60,80             .                                     |
 | ::::::: 20,40             : Power                               |
 |_________________________________________________________________|
     |||||||||||||||||||||||||||                                   |

  Jumpers

    1: SCSI Enable/Disable   (Open: SCSI enabled, Closed: SCSI disabled)
       (On the IDE version, this enables or disables the IDE port.)
    2: Memory Enable/Disable (Open: Memory enabled, Closed: Memory disabled)
    3: MS0 (see below)
    4: MS1 (see below)
    5: Test Mem              (Open: Autoconfig, Closed: Don't autoconfig)
    6: Terminator Power      (Open: None, Closed: Supply +5V SCSI term power)

  Memory Size Configuration

  Memory Size  MS0     MS1      Chips Added To Sockets
  -----------  -----   ------   ----------------------

      2M       Open    Open     20,21,22,23

      4M       Closed  Open     40,41,42,43

      6M       Open    Closed   60,61,62,63

      8M       Closed  Closed   80,81,82,83