[Olympus] Fastbus Readout

[Alexander Kiselev]

  Hallo Christian,

> Philipp tested the maximum possible readout rates for the two fastbus crates. 
> These numbers are not the numbers we will get during experimental running, 
> because they are measured
> with no entries in the TDCs and it might be necessary to slow it down a bit 
> for stable running with data in the modules. We will do further tests to 
> investigate that during the next days.
> At the moment the readout rates for the blast1 fastbus crate (one DC half) is 
> about 5 kHz. The readout rate in the other fastbus crate (other DC half and 
> TOF) is about 2.6 kHz.
> If one were to move one ADC and one TDC from the blast2 crate to the blast1 
> crate, the whole system would run with about 3.1 kHz.

  I must say this is misleading. I suspect not everybody involed in the 
discussion understands the exact meaning of these numbers. We will NOT be 
ever able to run with 5kHz *readout* rate. The only meaning of this 5kHz 
quote is: "average readout time of blast1 crate without WC hits is 
200us", right? 

  And then the actual on-tape readout rate and respective dead time will 
be determined by this number and the original trigger load. Say if this 
load is 1kHz, we will be writing to disk at ~1/(1000+200)us = 833Hz and 
therefore have ~17% dead time. At 5kHz trigger load we would apparently 
have 50% dead time and be writing to disk at 2.5kHz . And so on.

  Regards,
    Alexander.


> Again this numbers will get lower, when there are hits in the TDCs..
> 
> Regards
> 
> Christian
> Philipp
> -- 
> Dr. Christian Funke
> Helmholtz-Institut f?r Strahlen- und Kernphysik
> Nussallee 14-16 Zimmer 102
> 53115 Bonn
> 
> Tel. : +49 228 73-3598
> Fax  : +49 228 73-2505
> EMail: funke at hiskp.uni-bonn.de
> 
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