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 ���������
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disabled
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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.�