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 EXTOLL is a spin-off from the University of Heidelberg based on a long-running research project at the Computer Architecture Group (CAG) of the Institute of Computer Engineering. CAG has a long history of developing efficient interconnection networks for HPC. In 2003, as part of the University of Mannheim, the ATOLL (ATOmicLowLatency) network was presented. It implemented a 2-D mesh network for HPC clustering. This single chip solution provided a record-breaking ping-pong latency of about 3 µs.



In 2005, work on the EXTOLL project began at CAG. The first revision of FPGA-based prototypes have been in use since 2009 and demonstrate the performance capabilities of the architecture. In particular the low-latency and very high message rate were shown on the micro-benchmark level. Other communication functions also exhibited very high performance. For example, MPI_Barrier performed very well on the prototype platform. On the application level, it was shown that a large number of MPI applications run correctly on the network. Depending on the application characteristics, they also benefited from the superior characteristics of the EXTOLL network. In 2010, funding and support for a start-up company was provided by the German Federal Ministry of Economics and Technology program “EXIST Forschungstransfer”, and in 2011, EXTOLL GmbH was founded. In the same year the first FPGA-based adapter cards, Ventoux and Galibier, were introduced.