This Arduino is the predecessor of the Arduino UNO, it differs by having a different USB interface chip (FTDI FT232RL) and a slightly better power selection circuit (selecting between different power supplies available to the Arduino) - see Sarah Mitchell's very good electricalflux.com page referenced below.

So in some ways superior to the UNO, it does have a deficit in that the bootloader takes up 2k vs 0.5k of the available 32k of onboard flash ram. It is possible to use an ISP programmer to replace the bootloader code

• Info and comparison with UNO

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