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Entry  Wed Jan 7 02:54:09 2015, Jenne, Update, LSC, Fiddling with DARM filters DARM_design_orig.pdf
    Reply  Wed Jan 7 09:44:33 2015, ericq, Update, LSC, DARM phase budget DarmPhaseBudget.pdfDarmOLGresidual.pdf2015-01-DARMphase.zip
       Reply  Wed Jan 7 13:39:42 2015, Chris, Update, LSC, DARM phase budget 
Message ID: 10868     Entry time: Wed Jan 7 13:39:42 2015     In reply to: 10864
Author: Chris 
Type: Update 
Category: LSC 
Subject: DARM phase budget 

I think the dolphin and RFM transit times are double-counted in this budget. As I understand it, all IPC transit times are already built in to the cycle time of the sending model. That is, the sending model is required to finish its computational work a little bit early, so there's time left to transmit data to the receivers before the start of the next cycle. Otherwise you get IPC errors. (This is why the LSC models at the sites can't use the last ~20 usec of their cycle without triggering IPC errors. They have to allow that much time for the RFM to get their control signals down the arms to the end stations.)

For instance, the delay measurement in elog 9881 (c1als to c1lsc via dolphin) shows only the c1lsc model's own 61 usec delay. If the dolphin transfer really took an additional cycle, you would expect 122 usec.

And in elog 10811 (c1scx to c1rfm to c1ass), the delay is 122 usec, not because the RFM itself adds delay, but because an extra model is traversed.

Bottom line: there may still be some DARM phase unaccounted for. And it would definitely help to bypass the c1rfm model, as suggested in 9881.

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