CocoMEM Jr.


When The TANDY Color Computer 3 arrived, it included a simple but powerful memory management unit (MMU) to better support the expanded memory available in the Coco3.  Unfortunately, this additional functionality could not be added to the Color Computer 1, 2, or Dragon machines.

Until now.

The CocoMEM Jr. memory expansion unit adds Coco3-compatible MMU capabilities to your TANDY Color Computer 1, 2, and Dragon systems.  Plugging into the M6809 socket, CocoMEM Jr. allows non Color Computer 3 owners the expanded memory and MMU functionality previously unavailable.

Still in development, the CocoMEM Jr. already supports the following features:

  • Hardware support for 2 MB of system RAM (development units have 512kB of RAM installed)
  • 8 bit task registers
  • Support for 32 CPU MMU tasks, each with their own set of task registers
  • Support for 256 CPU MMU “tasklets” per task, each with their own set of task registers

Additional immediately planned features:

  • 16 bit task registers
  • Hardware support for 64MB of system memory
  • Per task bank write protect capability
  • Per task bank CPU read interrupt
  • Per task bank CPU write interrupt
  • “Move” 8kB segments of main memory around within the first 64kB of memory space
  • 512kB “emulation” mode (on Barry Nelson’s request)
  • NoCan3 $ff9b bank register support


  • One of:
    • TANDY Color Computer 1
    • TANDY Color Computer 2
    • Dragon 32
    • Dragon 64

CocoMEM Jr. units are currently in development, but will be sold in the  RETRO Innovations Online Store.

Units come with a 30 days return policy and 1 year warranty.

Technical Details

CocoMEM Jr. sits in between the M6809 CPU and the Color Computer motherboard, intercepting memory access requests and redirecting them to on board memory.  While it cannot redirect VDC memory requests, it can allow on-board memory and CocoMEM Jr. memory to co-exist.  As on the original CocoMEM, a second MMU task register memory block is used to store MMU configurations.  Please visit the CocoMEM page for more detail information on MMU operation.



Project Files

Frequently Asked Questions