The Active Rob Complex: An SMP-PC and FPGA based solution for the Atlas Readout System

The Readout System of the Atlas detector trigger requires receiving and latching of data on 1530 links with a bandwidth of up to 160MB/s per link, passing them to the processing nodes on request. This paper presents the Active Rob Complex (ARobC), a possible Readout System architecture, based on a low cost Symmetric Multiprocessor System (SMP) with a substantial CPU and I/O capacity, assisted by FPGA co-processors handling the large input bandwidth. With its computing power and the ability to group many input links the ARobC is a cost effective solution for the Atlas Readout System. Beside the original dataflow tasks it offers preparing and pre-processing of event data in real-time. Using FPGA co-processors for receiving and immediately storing the event data reduces load and internal communications of the ARobC. The current implementation comprises an SMP-PC with two PCI buses and four commercial FPGA based PCI cards “microEnable” equipped with SLINK input. A software library provides easy access to the FPGA hardware and optimizes the internal communication via PCI bus. Measurements demonstrate the ability to handle fragment requests internally with up to 70kHz @ 1kB, using Windows NT or Linux and the multithreaded software in an evaluation setup.