GameCube:SD Gecko and SD2SP2
As the GameCube's EXI buses (used for memory cards and serial ports, among other internal functionality) are based on SPI, other SPI devices may be connected to it.
SD and MMC cards are no exception; in fact, Nintendo officially released the DOL-019 adapter to connect a first-generation SD[1] to a memory card port, for the use of two compatible titles[2] for screenshots and data exchange - in Japan only.
(Note that this does not mean SD cards and memory cards are interchangeable; software must explicitly support SD cards, and more specifically the technologically different SDSCs and SDHC+s. Only recently did Swiss add memory card emulation features.)
The DOL-019 contains no electronics apart from noise filtering, and eventually clones started appearing under a variety of names: the WiiKey SD Adapter, the Datel SD Media Launcher (bundled with a boot disc), etc - eventually getting the umbrella term SD Gecko. The unfiltered clones (all but the Datel) even became preferable due to being compatible with double speed 32 MHz operation.
The SD Gecko quickly became the preferred storage device for homebrew, even continuing to hold this status at the very beginning of the Wii scene before widespread support for the internal SD slot became available.
In mid 2019, the SD2SP2 was launched. It is effectively a miniature SD Gecko fitting under the console in the ordinarily unused Serial Port 2, therefore avoiding the use of one memory card socket with ensuing functional[3] and cosmetic advantages. Homebrew software does not need dedicated programming support the SD2SP2 (unless it offers manual device selection), however it must be compiled with a sufficiently recent version of libogc or equivalent, therefore leaving older programs behind.
As the SD2SP2 is still just a mechanical adapter, variations on the theme exist including a side-loading version exploiting the small cutout on the side of the GC, and hardwired versions for full size slots and/or SP2-less consoles.
Notes
- ↑ An SDSC up to 1 GB. Larger non-HC cards can be used if repartitioned to 1 GB, as can be done by the two mentioned games.
- ↑ Animal Crossing e+ and Pokemon Channel
- ↑ Two memory cards can be simultaneously used again... or even a memory card + SD Gecko combination to try the above games' SD features while running a backup copy off the SD2SP2!