What are the differences between the NXT and the RCX? What are the differences between the NXT and the RCX? I know that the NXT is newer, but what features does it have that the RCX doesn't have, and vice versa (if the RCX has features that the NXT doesn't)?
NXT
RCX




3 motor and 4 sensor ports
3 motor and 3 sensor ports


Has encoders integrated in its motors so that they can be used as servos
Would need an additional rotation sensor on a sensor port to use as servos


Uses RJ12 connectors with the latch offset to one side
Uses regular 9V connectors (2x2 with metal in studs)


Uses a direct USB cable or Bluetooth for connection
Uses infrared to communicate with PC via an IR tower connected by a serial (1.0, 1.1) or USB (2.0)


Graphical 100X64 matrix display
Small numerical display with many limits


Technic oriented - uses technic pieces (no studs)
System oriented (studs) with small amount of technic


Uses graphical programming language with many features1
Uses a limited graphical programming language (apparently can't even run on XP)


Can play 8Khz wav files
Can play simple tones


Uses 6 AA batteries very quickly
Uses batteries more slowly


256 KB of flash memory that can hold a max. of 64 files of varying types
32 KB of RAM that can store up to only 5 programs





The original 1.0 version of RCX Brick had a 10v connection plug, but this was dropped from the later versions included in the Robotics Invention System 1.5. The NXT can use a rechargeable battery in place of the six AA batteries, and the rechargeable batteries also have a 10v transformer plug.

RCX retains its memory (including firmware) for a very limited time when not powered, just enough to change batteries. NXT uses flash memory and keeps it all when not powered.


1: Note that even powerful computers have trouble running big programs, and can easily mess them up. There exist many third-party systems for both RCX and NXT. Full list on Wikipedia.