I tried the ID software, and it seemed to like it. I never did get it working with that cable, but it seems that it was an issue with the 5V (despite using 2 different laptops and a desktop)
When I tried the CP2102 cable. It didn't work with 5V connected to 5V, but it did work with 3.3V connected to 5V, as r.cade mentioned.
It's now loading Amiga games!