Downlink rates The next slide was presented to Jonathans’ flux review It was based on the UW background runs, for which the generated and trigger rates are available, and which sampled a full orbit-day at 10%. An important parameter: downlink limit is 1.2 Mbit/sec (average). THB C&A presentation 12/12/05

Simulating rates: the big picture Incoming rate into the 6 m2 sphere: is it right? Corresponding trigger rate: implies 15% deadtime: too high! Downlink rate: saturates our bandwidth allocation? one full day THB C&A presentation 12/12/05

The downlink rates from the SLAC/Lyon 1B background run Note: it was not a full day If we throw out “no-cal” events here, rather than later, save a factor of two THB C&A presentation 12/12/05

What is the limit? Are we in trouble? Depends on amount of event data (including noise, which for the tracker is probably overestimated) JJ’s skill at lossless compression Current status, from JJ, via Atwood: OVERHEAD: ~12 bytes (fixed)   GEM: 40 bytes (fixed) (a little work could bring this done to <20 bytes, I'll do it at some time cause its cheap)   ACD : 7 addressing bits            5 bit hit mask (The 5 bits are-> Hit A:B side. Pha Accept A:B side, GEM Veto hit)            12 bits for each PHA side (up to 2)            example: A tile with only one PHA reporting in: 24 bits                          A tile with both       PHA's reporting in: 36 bits CAL: 32-64 bits overhead        : 4-5 bits addressing / log        : 12:17 bits for the ADC value /log (both ends)           [Empirically I am measuring about a factor of 2-2.25 compression over the data encoding           of  16 towers * (32 bits + 32 bits * nlogs)]           Example 50 logs::  64 + (5+15) * 50 bits => 133 bytes TKR: 12:13 bits per strip address           5-6  bits per TOT           Example 100 strips::         100 * 18 bits => 225 bytes THB C&A presentation 12/12/05

OK, these are (almost) linear in the number of DIGIS: what do we see for these events? THB C&A presentation 12/12/05

Apply the JJ analysis Event size analysis All events NoCal n bits   All events NoCal n bits total tota overhead 1.0 480 ACD 1.8 30 54 0.8 24 TKR* 9.8 18 176 6.7 121 CAL 19.0 20 380  20  0 1090 625 *TRK is overestimate, assuming 1 TOT/hit THB C&A presentation 12/12/05

The bottom line Preliminary! 1.2 Mbits/s / 1.1 kbit/event = 1.1 kHz event rate Preliminary! THB C&A presentation 12/12/05