MAD Expander Slot Box
This page was last modified 14:53, 13 January 2022 by Mars2000you. Based on work by Gdx.



The MAD Expander Slot Box was sold in Japan until recently.

Two models were available: one with three slots and one with four. Now both models are not available and will no longer be manufactured.

The four slots model has an expansion bus in extra, which is usable as slot 3 only on MSXs that not use this slot (otherwise, it can only be used as an I/O slot).

Price: 18,600 yen (3 slot model), 24,800 yen (4 slot model)


MAD Slot Expander Box 3 slot
MAD Slot Expander Box 4 slot
MAD Slot Expander Box cartridge (BUF-B)


Model with 3 slots (MXE-MAIN-A)

  • 3 cartridges slots

Model with 4 slots (MXE-MAIN4-A)

  • 4 switches to disable or enable the corresponding slot.
  • 4 cartridges slots
  • 1 expansion slot (Can be used as I/O slot, or slot 3 if this slot is not already used by the MSX)
  • 1 connector for power supply input 12V, 2A
  • 1 power supply output 12V, 2A
  • 2 female USB ports type A (Can be used to power 5V peripherals when the MSX is turned on)

Note: You can use the Extension circuit board MPC-FC50P4 in the expansion slot.