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Phase I Latency Envelopes – an update

Phase I Latency Envelopes – an update. Norman Gee. November 2013. 1. Caveat. The spreadsheet calculation has never agreed with the measured numbers Of course Thilo’s measurements are right and the spreadsheet is wrong Need to understand the differences – more on this in a moment

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Phase I Latency Envelopes – an update

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  1. Phase I Latency Envelopes – an update Norman Gee November 2013 1

  2. Caveat • The spreadsheet calculation has never agreed with the measured numbers • Of course Thilo’s measurements are right and the spreadsheet is wrong • Need to understand the differences – more on this in a moment • The update I did for a recent L1Calo meeting showed only about 5BC of spare latency remaining • I recovered some latency for Upgrade Week by better modelling of CP, JEP, L1Topo and CTP • These have multiple inputs and/or outputs at different times • E.g. CTP has electrical into CORE, electrical into Input modules, Optical into CORE, all with different latencies • The spreadsheet version used here is a working version intended to give the latest estimate, it is not yet stable enough to be uploaded into EDMS Latency - N. Gee

  3. Latency - N. Gee

  4. Comments • The calculation shows remaining spare of ~ 10BC, but this is for Run 3 and probably should not match Thilo’s Run 2 number • I am not sure that high-speed link latencies are as long as they need to be, including multiplexing • The multi-Gbit signals we have running are typically 5BCs, some of the tables still have 4 BCs. • Muon/Tile-D-layer interface is not yet included and needs to be added • Optional gFex is not included • Barrel Muon trigger is not well modelled, using measurements instead(Riccardo is trying to get a breakdown) Latency - N. Gee

  5. Measurements • I would like to get the calculation right • Opportunity while ATLAS is in pieces/being rebuilt • Already started discussions of measurements inside current L1Calo before and after the system is changed • E.g. measure longest cable by TDR while Tilecal is disconnected • Will also ask Muon colleagues to help re-measure installed & new muon components • I am still concerned that I don’t know the whole story, I fear we will be close to the limit, real latencies are always longer than estimates • There will not be another big optimisation like the one I have just done • Watch this space… Latency - N. Gee

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