Highly Scalable
Packetised
correlators
Jason Manley
CASPER workshop 2009
Contents
•
Where we’ve come from
•
CASPER
•
Correlator design
•
Dataflow
•
Engine operations
•
Scalability
•
Present and future deployments
In the beginning…
Computing
backend
Analogue
processor
Control &
Monitoring
Big
dish
Interferometry
…
ATA
Green Bank 300ft
…more recently…
EVLA
baseline
board
(Carlson, 2006)
CASPER
Center for Astronomy Signal Processing and Electronics Research
•
Open
-
source, collaborative environment
•
Reusable, platform
-
independent
gateware
•
Modular, upgradeable hardware
•
Low instrument NRE, shared by the community
•
Enables rapid development (8 instruments / 2 years)
•
Industry standard communication protocols
•
Low Cost
CASPER DBE concept
CASPER DBE concept
Clocking
•
Clocks:
•
Locally synchronous, globally asynchronous.
•
Sampling clock synchronized at F engines.
•
X engines each run off independent local clock.
•
Synchronized using global 1pps signal at ADCs
•
Propagated to X engines using out
-
of
-
band signaling on XAUI links.
•
Headers labeling and
timestamping
10GbE Ethernet packet data.
Correlator
Overview
How does it scale?
1
10
100
1000
10000
100000
1000000
F Engines
X Engines
43
100
200
330
760
0
100
200
300
400
500
600
700
800
1998
2000
2002
2004
2006
2008
2010
Logic Cells (thousands)
Xilinx
Virtex
Family
•
Processing power doubling every two years
•
V4 = ½ power requirements of V2Pro*
* Manufacturers claim
-
Xilinx Inc.
Existing systems:
PAPER
-
Green Bank
•
8 dual
-
pol
antennas, 150MHz.
•
1
st
Generation: one BEE2 & four IBOBs.
•
First deployment of packetized system.
•
Continuous upgrades.
Existing systems:
Northern Cross,
Medicina
, Italy
•
Designed and deployed in under 2 weeks.
•
32 single
-
pol
antennas, 32
MHz.
•
1
st
Generation:
•
one BEE2
•
eight IBOBs.
New deployments: KAT
-
7
•
7 dual
-
pol
antennas, 400MHz.
•
Pure ROACH.
•
New control and monitoring interface (KATCP),
coarse delay, high speed output (less than 100ms).
•
Expected early 2010.
New deployments: GMRT
•
32 dual
-
pol
inputs, 400MHz bandwidth.
•
Collaboration
–
shares design with KAT
-
7.
New deployments: PSA
-
32/64/128/256
•
PAPER in South Africa, staged deployment
•
Up to 256 antennas,
100MHz
•
Generation 1.5 (IBOB+ROACH) initially,
•
Generation 2.5 (ROACH + ROACH
-
II) eventually.
•
First field deployment of ROACH system.
•
Correlator deployment starting in January!
Jason Manley
jason_manley@hotmail.com
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