That is true, I did see that topic.
Partly my fault but I should have been more clear. The Duo as mentioned in that topic has the built in memory for the Super System CD card. A normal PC Engine with CD addon or Turbografx 16 with CD addon does not have any built in memory for that function. My hope was with the ram on the TED 2.4 it could be mapped for Super System CD or Arcade card use. Then I wouldn't have to swap the TED 2.4 and a Super System card in my Turbografx 16 + CD addon combo.