Looking to ROM dump just a handful of games, so I’m trying not to spend hundreds on a Sanni or Retrode. I saw this on AliExpress for $15.
I’ve personally had good luck with Alibaba and Aliexpress, but I recognize that this could just straight not work. There’s no documentation, but it claims the game data will show up like files on a USB flash drive.
Anybody know where this design came from?
You are correct.
One can solder in a temporary "helper battery" (or 3V power supply) to the same traces but in a different spot, to keep the SRAM alive while the real battery is replaced.
Some later games (GBA-era) use Flash memory and the battery is just for the clock.