[evla-sw-discuss] Simple subarrays: a modest proposal

[Bruce Rowen]

Just to jump in on the dumptrig stuff:

It may help to not think of the dumptrig originating from a particular Station board as needing anything to do with that station.
Think about using rack 8 to generate DTs for all the baseline boards and having the boards source the DT needed for that sub arrays dump schedule.

-Bruce


On Apr 1, 2014, at 2:41 PM, Michael Rupen <mrupen at nrao.edu> wrote:

> 
> For "real" (dynamic) recirculation I think DUMPTRIG is the only issue.[*]
> I am mildly worried that we haven't tried complex subarray setups, as that
> might task the CBE if e.g. five subarrays are doing different levels
> of stacking & recirculation, and (because we currently do BlB-by-BlB NIC
> assignment) those wind up at the same NIC and hence use the same CBE node.
> If we allow faster dumps than normal because of the smaller number of
> baselines I can imagine this becoming problematic.  Hence the idea that
> we might have to write down some simple restrictions, at least until we've
> extensively tested the options we wish to offer.
> 
>             Michael
> 
> * On the DUMPTRIG end, apart from the StB-based restrictions, there are some
>   limitations on how DUMPTRIG is routed from StBs to BlBs.  We don't run
>   into this much for "regular" observing because we can basically use
>   just one antenna's DUMPTRIGs; with subarrays we start having to
>   exercise more sophisticated routing.  Sonja and I discussed this (I
>   think you were involved??) in the context of how many DUMPTRIGs we
>   could have total, if we started wanting the limiting case of one
>   DUMPTRIG per subband...there were magic factors of two involved (above
>   the obvious 16), and various things she could in principle fix up in
>   the CM.  [The implication is that these are really CM rather than
>   hardware limits.]  I don't think she got very far with that, as it was
>   not a high priority at the time, but I don't recall the details right
>   now.  Being me I probably have some of this in various e-mails, but it
>   would take a while to find them.  Let me know if you're interested.
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