NOTE: production rev2.0 Mem+ PCB’s are now available; I will be updating this product page RSN. Due to additional components required for the new features the kit and assembled and tested prices will be increased.

Mem+ Photo #1

Mem+ board:

  • Four sockets for 512KB memory chips for 2MB per board
  • Jumper for selecting board address range ($000000-$1FFFFF,$200000-$3FFFFF,$400000-$5FFFFF,$600000-$7FFFFF)
  • raises PropPlug compatible programming pins for CPU #1 to Mem+ for easy access
  • ONE of the Mem+ boards installed in a stack may implement one or more of the following optional features
  • MAX3232 based serial port / programming port
  • optional RESET transistor
  • disable reset jumper
  • selectable DTR/RTS for reset
  • DB9 PCB mount footprint
  • CP23S17 SPI I/O expander
  • uses four available pins of CPU#1
  • 16 parallel I/O’s brought out to 2×5 ten pin headers with GND and 3.3V
  • may be used for Atari/Sega style joysticks
  • SD card interface, uses other four available pins of CPU#1

Mem+ Parts list with PCB placement

More on the memory and bus design:

  • 24 bit addressing
  • page address is latched from P0-P15 when P26&27 are both pulled low
  • P26 is ~RD
  • P27 is ~WR

Memory Map:

  • addresses $000000-$07FFFF reserved for memory mapped I/O
  • on-board 512K ram addressed at $200000-$27FFFF, but “mirrored” thru $37FFFF
  • $400000-$5FFFFF nominally for first Mem+ board
  • $600000-$7FFFFF nominally for second Mem+ board


You can have 7.5MB of memory in your Morpheus Stack by using four Mem+ boards as follows:

  • select address range starting at $000000 for the first Mem+ board
  • DO NOT POPULATE first socket as its address space is used for I/O
  • populate remaining three sockets on that board
  • select address range starting at $200000 for the second Mem+ board
  • remove the 512KB memory chip from Morpheus, populate all four memory sockets on second board
  • select address range starting at $400000, populate all four sockets
  • select address range starting at $600000, populate all four sockets

A second view:

Mem+ Photo #2

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