Chad's email:

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  Anyways, I was wondering if you could slap together a program to test the
  bankswitching code.  I basically implemented your suggestion.  Namely,
  writes to 0x0040 to 0x005F are loaded into the bankswitch table, with the
  following simple mapping:

      0x0040          0x0000 - 0x07FF
      0x0041          0x1000 - 0x17FF
      ...
      0x004F          0xF000 - 0xF7FF
      0x0050          0x0800 - 0x0FFF
      0x0051          0x1800 - 0x1FFF
      ...
      0x005F          0xF800 - 0xFFFF

  where the number on the left is the address to which you write the remap
  bits, and the numbers on the right are the window (as seen from the intv)
  that will be remapped internally by the SX.  So to remap 0x5000-0x57FF in
  INTV space to 0x1000 - 0x17FF in Intellicharger RAM space, you'd write
  0x0010 to address 0x0041.  I guess that implicitly states what I haven't,
  which is that the remap bits are grabbed from the lower 8 bits of the
  written data.

  Of course, to allow this remapping to occur, you'd have to set the remap
  enable bit for 0x5000 to 0x57FF when the enable tables are downloaded to
  the SX.

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Additional details:

 -- The remapping works by XORing the 8 bit value that was written to
    the bank-switch register with the 8 MSBs of the address.