The R4, and the M3DS simply which was basically the same thing, rose up to be the most popular of the earlier DS slot flash carts. I am not sure why this happened as it was not the best featured or most compatible, however I suppose it was cheap enough and very easy to use. It was popular to the extent that R4 was a shorthand in some circles for DS flash cart (see also jailbreak when people mean hack and the whole thing with generic trademarks), and loads of people cloned it or if they made a flash cart it was then called R4 something (dual core, gold, king, pro..... it got ridiculous). Even the big teams got in on the action and released things under an R4 like name.
However either through a lawsuit or through something else the original R4 team dropped support for new games. Its name was then mud and as there was lots of stock then you could pick up one, or a clone, for next to nothing. Oh and it only supported SD (up to 2 gigs) which was not ideal with the newer DS games taking up more and more space.
Wood, which branched from the AKAIO/acekard RPG source base at some level (AKAIO generally being the source for many fixes and probably the best thing available, give or take a lack of support for some of the crazy features like savestates and in game text readers, its cheat engine was top notch though), gained support for the R4 after the R4 clone makers kit did the rounds. Wood also supports one of the other things with R4 in the name but I forget which at this point. Wood was not the first thing a third party tried to try to drag the R4 into better support but it was a straight up replacement for the menu and as simple as anything else in flash cart world to operate.
There was something of a lag between Wood supporting the R4 and flash cart vendors catching on to this so it was quite possible for people to have a DS/DS lite compatible flash cart that played all the games for next to nothing. Or to buy an old R4 that someone might have ignored due to the lack of support and stuck in a drawer.
DS slot flash carts and the 3ds.
If you want a more technical overview of the situation then http://hackmii.com/2010/02/lawsuit-coming-in-3-2-1/
If you can hack your 3ds at the firmware level (so with gateway, the browser thing and possibly cubic ninja, all will require firmware 9.2 and older) then anything that once worked on the 3ds can work again. http://gbatemp.net/threads/release-use-blocked-ds-flashcards-on-3ds-probably-n3ds-too.376719/
If you are going on a stock 3ds then your options are more limited. Fortunately the main two options are the supercard DStwo which is a great cart, if a tiny bit more power hungry than the average flash cart and also expensive when you can find it, and I think it was the R4i gold which plays basically everything. The DSTwo stopped being made and stock dried up some time before Christmas though so they are hard to find these days, there was supposed to be the DSTwo+ out at some point but we have not heard anything about that for a while.
However either through a lawsuit or through something else the original R4 team dropped support for new games. Its name was then mud and as there was lots of stock then you could pick up one, or a clone, for next to nothing. Oh and it only supported SD (up to 2 gigs) which was not ideal with the newer DS games taking up more and more space.
Wood, which branched from the AKAIO/acekard RPG source base at some level (AKAIO generally being the source for many fixes and probably the best thing available, give or take a lack of support for some of the crazy features like savestates and in game text readers, its cheat engine was top notch though), gained support for the R4 after the R4 clone makers kit did the rounds. Wood also supports one of the other things with R4 in the name but I forget which at this point. Wood was not the first thing a third party tried to try to drag the R4 into better support but it was a straight up replacement for the menu and as simple as anything else in flash cart world to operate.
There was something of a lag between Wood supporting the R4 and flash cart vendors catching on to this so it was quite possible for people to have a DS/DS lite compatible flash cart that played all the games for next to nothing. Or to buy an old R4 that someone might have ignored due to the lack of support and stuck in a drawer.
DS slot flash carts and the 3ds.
If you want a more technical overview of the situation then http://hackmii.com/2010/02/lawsuit-coming-in-3-2-1/
If you can hack your 3ds at the firmware level (so with gateway, the browser thing and possibly cubic ninja, all will require firmware 9.2 and older) then anything that once worked on the 3ds can work again. http://gbatemp.net/threads/release-use-blocked-ds-flashcards-on-3ds-probably-n3ds-too.376719/
If you are going on a stock 3ds then your options are more limited. Fortunately the main two options are the supercard DStwo which is a great cart, if a tiny bit more power hungry than the average flash cart and also expensive when you can find it, and I think it was the R4i gold which plays basically everything. The DSTwo stopped being made and stock dried up some time before Christmas though so they are hard to find these days, there was supposed to be the DSTwo+ out at some point but we have not heard anything about that for a while.
