ATLAS RoI Builder + CDF

● Brief reminder of ATLAS Level 2● Opportunities for CDF (what fits - what doesn't)● Timescales (more of what fits and what doesn't)

Conclusions from quick tour of ATLAS TDAQ

● ATLAS Level 1 looks very much like CDF Level 2– hardware based clustering, energy sums, isolation and

muon Pt

● Level 1 accept rate for ATLAS is similar to that for CDF (~50-100 kHz)

● RoI Builder (RoIB) plus Supervisor processors could act in the same capacity as the alphas do in CDF– same transaction rate (L1A rate)– provided the decision code is simple Supervisors could

make the full level 2 decision instead of I/O to LVL2 farm

CDF != ATLAS● Input to RoIB is via S-link

– this is different from CDF Run IIa but not different in IIb

● Latency in ATLAS Level 2 is enormous– buffers are ~1000 events deep not 4– RoIB latency is a non-issue for ATLAS

● initial prototype of RoIB waited for all event fragments to arrive before sending - this alone would introduce unacceptable latency for CDF it also limits size of L1 RoI data (since this needs to be buffered in the RoIB)

– Level 2 decision order is different from the L1A order

Potential CDF Level 2● Single Builder

and input card● 4 processsors

– could be more

● Output of trigger decisions to PULSAR is probably reasonable, but not necessary

Beginning to look at simulation

Still too infantile but...

40kHzlivetime 86%

Latency in microseconds

Current Architecture

4k x 36bFIFO

S-L

ink C

onnector

GbEMAC

LSI L8101

GbE SerDesAgilent HDMP-1636A

Opt.Conn.

Features– Large input FIFO– Large Buffer– Optical GbEthernet Physical

layer– Conforms to S-Link specs– FPGA can do data alteration if

needed

512k x 32bMemory

FPGA

ATLAS plan/timescale

● The current plan is to produce a prototype early this year (~April)

● There is already a 12U prototype (has been for several years) which demonstrated 100kHz operation

● 9U prototype system will include the ability (important for CDF but not necessary for ATLAS) of “routing” as opposed to “store and forward” type operation

Conclusions

● Appears reasonable to think of RoIB as merging unit for CDF– Still work to do in demonstrating that this idea

actually makes sense (same work needed for any other merging scheme)

● Next steps should work out dataflow (how much from which sources and including as many of the overheads realistically as possible)