A3640 Reference

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  The A3640 is the stock 68040 processor board that comes with most A4000s.
  It contains a 25 MHz 68040; some boards came with the 68LC040, which is a
  68040 with no built-in math coprocessor functions. The A4000 User's Guide
  has instructions on upgrading from a 68EC040, which has no math coprocessor
  or memory management unit (if any A4000s were ever shipped with 68EC040
  processors, there were very few of them). Revision 3.1 or 3.2 boards with
  U209 marked as "-02" or "-03" can be used in A3000 or A3000 tower
  computers. (For more information on A3640 board revisions and bugs, see
  Internals/Definitive Buster.)

  The "cut and jumper" patch mentioned by Dave Haynie in the Definitive
  Buster section is: lift pin 6 of U200, and short pads 6 and 7 on U200.
  This, in combination with an upgrade to the U209 PAL, converts a 3.0 board
  to 3.1. The only difference between 3.1 and 3.2 boards is another upgrade
  to the same PAL.

  Information on PAL upgrades can be found at:
    ftp://iaehv.nl/pub/users/paul/amiga/A4KPALS.LHA

  (See also Tips/Processor Board Mounting.)

  Jumpers

    J100: Enable *CacheDisable *MMU Disable
          1-2 Closed and 3-4 Closed: Enable CDIS* MDIS* (caches and MMU
                                     disabled at powerup and reset: default).

    J400: Enable MAPROM: Enable remapping circuit for loading Kickstart
          into Fast RAM with a developer utility program.
          1-2 Closed: MAPROM enabled (default).
          3-4 Closed: MAPROM disabled.