Green Bank Ultimate Pulsar Processing Instrument / Puerto Rican Ultimate Pulsar Processing Instrument. These are the current (started recording in 2014/2015 for GUPPI/PUPPI) data recording (backend) instruments at Arecibo and Green Bank, respectively. They are made up of analog to digital converters (ADCs, also known as samplers), field programmable gate arrays (FPGAs), and computer servers with graphical processing units (GPUs). GUPPI/PUPPI are capable of recording data in multiple modes, but for NANOGrav observations they sample, coherently de-disperse, and fold the incoming data using the observed pulsar’s par file across up to 800 MHz of bandwidth.