About a fortnight ago we mentioned in passing that a group of homebrew development enthusiasts had managed to get something to appear on the Nintendo DS handheld using a pass-through.
Now it appears that a chap going by the name of DesktopMan has gone one step further, emulating Tetris and getting it to display on both of the console's screens. According to the author's comments, the emulator, which hasn't been released yet, runs on a real DS via pass-through.
The pass-through is currently the only method of running homebrew code on the DS and uses a cable going into the DS game card slot as well as a GBA Flash cart in the GBA cartridge slot to load any programming.
As far as we can see, it works by hijacking the transfer of commands between DS game card and DS hardware immediately after a reset and using a modified header to command the handheld to look to the GBA cartridge ROM.
DesktopMan seems to have used this process to allow an emulated version of Tetris to run on the DS as you can see from the photograph on The Mod Gods website here.
There is talk of eventually eliminating the need for the clunky board-and-cables arrangement that helps plug the handheld into a PC - by "replacing a BGA chip inside the DS" according to NDSTech Wiki - but for the moment attentions are focused elsewhere.
To learn more about Nintendo DS homebrew activities, there are plenty of interesting sites listed on the side bar of The Mod Gods website, including the previously referenced DS Linux project.