These are the devices used to store the licensed developer’s work in progress images or store downloaded commercial games, since there is no rewritable medium with Nintendo DS. These were usually known as flashcards, the older flashcards used SLOT2 (the GameBoy Advance Game Pack Slot) and newer cards use SLOT1 (the DS Game Card Slot).
The newer devices like R4 for the DS, Acekards (Ver. 2, 2i, RPG) and DSTT are very popular. Acekard 2 was rated 90% better choice than any other card by the users and even won a Golden Gbatemp award. Some of its features were 100% Game compatibility, download play support, skinnable, very swift loading, micro SD/SDHC card support and Action-Replay cheat support. Due to a game freeze bug, Acekard 2.1 version was launched and did not lack any such issues.
Acekard team was the first team to release a card compatible with Nintendo DSi and they called it Acekard 2i. It was similar to Acekard 2 but supported DSi. Later, a newer version of DSi was launched which was made compatible to Acekard 2i by downloading a patch. A patch was also released to handle the compatibility issues with 3DS model and now Acekard 2i can be used by it in DS mode. Acekard R.P.G was launched with a strong firmware and many cards are based on its firmware. A device that featured both a Micro SD slot and NAND memory, it uses SDHC cards which support from 4GB to 32GB and is bundled with a mini USB cable to connect the card with a computer to access 1GB of internal NAND memory.
DSTT is a very popular card compatible with SDHC and is versatile beyond simply playing homebrew and ROM software. One of the most powerful and useful features is that they incorporated the cheat support in variety of games. DSTTi was tested and reported to work with DSi XL console and was released in March 2010. The Official DSTT and DSTTi TT Menu kernel was updated to V1.18. Another data card R4 for the DS is a Slot1 memory solution that used Micro SD card for storage and final firmware versions included Auto DLDI patching, download play support, Action Replay Cheats and support for Nintendo Wi-Fi connectivity. The R4DS was updated in 2007 in its design where the spring mechanism was replaced by manual loader of memory card due to complaints.