• Measured FED data throughput from the slink to the FEROL using FED firmware v18.4 that features a parallel draining architecture of the FED input channels.
  • The system is driven by the Pixel FED Tester which allows one to apply a variable hit load per event to the FED input channels. The trigger rate is set to 100kHz. Throttling of the input trigger rate can be caused by back-pressure in the readout chain (FED or FEROL).
  • Solid line is the measured throughput, while the dotted line is the measured trigger rate.
  • The blue (red) triangles are the throughput of simulations with a pile-up of 70 (130).
  • Starting from a hit load larger than 6 hits/ROC/ch, the FEROL is saturated resulting in a constant data throughput of 7.5Gbit/s. At the same time the trigger rate starts to get throttled (dashed line decreases from 100kHz). FED itself is not the bottleneck in this setup.
  • The mismatch between the factor of increasing event size (e.g. doubling the size from 6 → 12 hits/ROC/ch) and decreasing trigger throttling (100kHz → 74kHz) comes from a realistic emulation of the detector frontend in the Pixel FED Tester that truncates too large events.

-- BenediktVormwald - 2020-02-10

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