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APSR: A New Baseband Recorder with an in-built Supercomputer

The ATNF Parkes Swinburne Recorder (APSR) is a next-generation baseband data recording and processing system developed in collaboration between Swinburne University of Technology and the Australia Telescope National Facility (ATNF).


The APSR hardware consists of:

  • the Parkes Digital Filter Bank (PDFB3), based on two Compact Array Broadband Backend (CABB) boards;
  • two Cisco 3750E high-performance commercial network switches; and
  • a Beowulf-style cluster of 20 Dell 1950 server-class machines, each with dual quad-core Intel Clovertown processors, 16 GB of RAM, and 1.5 TB of disk. A third switch connects to the Dell Remote Access Controller (DRAC) ports on each node to provide remote system administration capability.

The CABB boards perform analog-to-digital conversion of two dual-polarization signals, each with a maximum total bandwidth of 1 GHz. These signals are sub-divided in frequency using a polyphase filter bank programmed into the CABB Field Programmable Gate Array (FPGA) logic blocks, and streamed to the cluster switches via four 10 GbE connections. The switches, in turn, deliver the sub-bands to 16 of the server-class machines via 1 GbE connections.


Once in workstation RAM, the data are:

  • routed, managed, and monitored using psrdada;
  • coherently dedispersed and reduced in real-time using dspsr; and
  • archived for later analysis using psrchive.

These three Open Source software projects are developed at Swinburne in collaboration with pulsar research groups around the world.


The major technical innovations of APSR include:

  • routing data via a commercial switch using conventional UDP streaming instead of specialized Direct Memory Access (DMA) hardware, a more cost-effective solution that facilitates the duplication of this system at other observatories;
  • processing data directly from RAM, thereby eliminating the disk I/O bottle neck;
  • exploiting the multiple core architecture of the Intel Clovertown chips and reducing cache requirements with multi-threaded data reduction software;
  • providing remote administration capability in preparation for future remote operation of ATNF observatories; and
  • professionally engineering the acquisition and analysis software under an Open Source license as part of our continuing dedication to foster international collaboration.

APSR will be an integral part of our intensive high-precision pulsar timing campaign. With 8 times the bandwidth (from 128 MHz to 1 GHz) and greater dynamic range (from 2 to 8 bit sampling) than our current instrumentation, APSR will yield arrival time estimates with at least 3 times greater precision than those derived from previous data.

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