Front of STARGATE 3DS.
It has a SmartFusion2 fpga and an Atmel sam d11 ARM processor.
My guess is that the Atmel chip has something to do with USB or SD card communication.
Back of STARGATE 3DS.
I initially thought it would contain firmware for DS MODE and 3DS MODE, but after dumping the firmware, it turned out not to be the case.
SPI flash = W25Q16JV WSON-8 6x5mm.
SPI flash labeled UP.
1. Contains an ASCII table at the beginning.
2. Almost empty.
3. I'm guessing it has something to do with the Arm chip.
SPI flash labeled DOWN.
1. Seems to be a firmware that covers both alex rider(ds) and 3ds.
2. It stores the location of the current 3ds file at 1FF000h.
I only dumped one cartridge, so I don't know if it contains any specific data.
The only thing I saw was 1FF000h, which recorded the location of the 3ds file.
Saving it to a file on the SD card would be a better way, but I don't know why it's writing to the SPI FLASH.
I've attached the dumped firmware.
If anyone is interested, feel free to compare or analyze the firmware.