Ah, RP2. On of the finest mods that ever came out of the fantastic modding scene around Minecraft. It was one of the four foundational mods in the scene: BuildCraft, IndustrialCraft (and later IC2), Better Than Wolves, and RedPower2.

Sadly, RP2 is dead, and with it the RP2 computer model, the likes of which will likely never be seen again (for those not in the know: most mincraft mods adding computers of some sort essentially allow scripting in some HLL, and maybe a primitive DOS-style prompt, akin to ComputerCraft. Not so in RP2. RP2 computers were actually full emulated 6502s, with a FORTH monitor built in (although you could, of course, write your own). This should give you an idea of what made RP2 so special). Except not quite, because Eloraam is now working on RP3, which will actually be its own game, because she got sick of putting up with MC's limitations. Knowing Eloraam, it will be done by 2030.