From: hallam@zeus02.desy.de (Phillip M. Hallam-Baker)
Subject: Re: SuperCollider "For" or "Against"
Reply-To: hallam@zeus02.desy.de
Organization: DESY ZEUS Central Data Acquisition
Date: Mon, 27 Jul 1992 16:54:02 GMT

In article <1992Jul27.142922.16831@dscomsf.desy.de>,
poser@vxdsyc.desy.de (Till Poser) writes:

|>In article <1992Jul26.110151.7363@dscomsf.desy.de>,
|>hallam@zeus02.desy.de (Phillip M. Hallam-Baker) writes:
|>
|>|>Summary:
|>
|>|>Mr Tice arguing from a single magazine article from two year ago
|>|>attempts to argue with a Postdoctoral research fellow in the field.
|>|>Readers may wish to savour the final paragraph from Mr Tice.
|>
|>
|>|>In article <01GMRRB8AWJK001E2U@utarlg.uta.edu>,
|>B645ZAW@UTARLG.UTA.EDU
|>|>(Stephen Tice) writes:
|>|>|>Interesting that you would leave out *operations and maintenance*
|>cost,
|>|>|>and are you using superconducting magnets?
|>
|>|>Yes, we have to, the electricity bill would be too high otherwise.
|>The
|>|>HERA ring is the first of it's type to use superconducting magnets
|>for a
|>|>proton ring. Our ring has a 6.3 Km circumference. You can scale up
|>the
|>|>costs from that.
|>
|>Just as an apercu here, Phill: 
|>
|>The whole configuration, i.e. DESY II and III, PETRA, DORIS and HERA
|>are
|>running on the same power outlet that was built 15 years ago for PETRA
|>|>alone. As far as I recall, this outlet is in the ~10 MWatt range,
|>but You 
|>had better ask one of the various HERA people. I know however, that
|>one
|>of the conditions for building HERA was that it was not to exceed the
|>maximum drain on the grid that DESY already was allowed by the City
|>of
|>Hamburg. The main reason lies in the fact that HERA was built in, or
|>rather under, an entirely residential area.

Till has local knowlege that means that he is much more authorative
here. I was initialy responding using figures I got from asking people
in the control room. I didn't exepect these to be precise, but I did
expect them to indicate whether the Tice $1 billion figure was
reasonable.

|>As to Tbyte/s <-> Tbyte/ns controversy (the latter amuses me somewhat),
|>ZEUS, pre First Level Trigger, has something between 300 and 500ks worth
|>of data, partially still in analog form, every bunch crossing and that
|>is every 96 ns. This makes the amount of Raw Data, before  data reduction, 
|>something like <5 Tbyte/s. After three levels of triggers that is reduced
|>to 1-2 Mbyte/sec.
|>
|>If I take a WAG of a scale factor of 10 between the number of ZEUS data 
|>channels and the number channels of an SSC detector and allow for a bunch 
|>crossing rate of 60 Mhz, I arrive at somewhere around 300 Tbyte. Assuming 
|>parallel and pipelined data reduction in various trigger levels, I don't see 
|>anything unfeasable with that number, even if I rely completely on existing
|>technology. If we take the ZEUS solution, we'd just plug in another couple
|>of hundred Two-Transputer-Boards into the Second Level Trigger, since ZEUS
|>is fully scalable, as far as I know. We'd have to pipeline them somehow, 
|>though. Comments, Phill?

I saw a proposal at CHEP where the SSC people showed a T9000 (successor
to the T800 transputer we use) based design which basicaly did the job,
of course I would hasten to add that this was merely done to show that
it was possible, they have a long way to go before any decisions are
made.

The transputer architecture seems to be very well matched to HEP  type
triggering. One of the main things that ZEUS has proven is the
usefullness of this design. For the SSC I would hope that we could
persuade one of the major manufacturers to knock something similar up.
DEC have been rumouring that they have a very fast design turnaround on
silicon nowadays, if they would stick some fast CSP communication
channels on an alpha chip I would be very interested. The same goes for
SUN, Intel and Motorola. This is the sort of industrial cooperation we
are meant to be pushing. Just liked we pushed companies into producing
fast backplanes, fast networks, huge and fast data storage and the rest.
If there is no more developments in computing in the next ten years we
could do it with todays technology from inmos though.

The real challenge lies right at the front end in the first level
trigger. This is not really my field. However I would want to start
talking to some oscilloscope manufacturers, they have faced all this
100MHz stuff and solved many of the problems. Looked at one way all that
ZEUS is is a huge, intelligent datalogger (oscilloscope).

Till's figure for the data rate is rather high, however as he says the
raw data rate is a pretty meaningless figure, most of the channels won't
get hit in a given event, thus it is fairly easy to reduce the data. The
SSC has many more channels, however the occupancy  is not going to
increase. One big change at the SSC is that unlike at ZEUS people are
talking about data compression in the initial design stages. We only
started worrying about that a couple of years back.


Phill Hallam-Baker