The Arduino UNO and Arduino Mega 2560 update the Duemilanove and Mega respectively. They now use an ATMega8U2 instead of an FTDI USB to serial converter chip. Allowing an Arduino to become nearly ...

Meanwhile, the Arduino Mega is getting the same USB chip along with an ATMega2560 processor with twice the memory. Right now only 128K is available, but that's a software limitation and they're ...

He has the processor, of course. But everything else — clock, memory, and power — are from an Arduino Mega 2560. You could argue that’s two chips, but the board actually has several chips on it.