Hi Ben,
About two years ago we experimented in getting maximum amount of data from
iBob to PC-based recorder, results are in
http://www.metsahovi.fi/en/vlbi/10gbps/index .
Getting data out of iBob or getting data into PC was not a problem,
although the udp packetizer took some work. Turns out that for
fixed-length udp/ip packets a constant pre-computed hesder can be used.
The disk speed was no big problem, but the raid driver tried to push
everything through one core which became saturated.
Using simultaneous udp receiving and disk writing (or any other
processing) on one PC was a problem since all of these were CPU-intensive.
Jan and Guifre managed to get consistent 4 Gbps by using several streams
and raid systems so that the tasks were evenly devided over all processor
cores.
I have seen a brochure from some small company claiming speeeds up to 8
Gbps, but they very carefully avoid saying if that's burst speed or
continuous speed.
Best regards,
Jouko
"Life is pretty simple: You do some stuff. Most fails. Some works. You do
more of what works. If it works big, others quickly copy it. Then you do
something else. The trick is to do something else."
On Sat, 7 May 2011, Ben Mazin wrote:
A quick question about getting data off the ROACH.
We have built a 256 channel narrow band channelizer for ROACH. Each channel
outputs complex I and Q data at 500 kHz, so when we want to stream the full
data rate we are using a 10 GbE port and UDP.
We are now implementing an on-board optimal filter and pulse detection
algorithm which will cut our data rate down drastically - probably to around
30 Mbits/sec. This is comfortably doable over a 1 GbE port, which would be
nice since we could avoid expensive CX4 hardware.
What are the highest data rates people have achieved getting data from the
FPGA through the 1GbE port on the powerPC? Did you use KATCP? Any tips on
setting up the FPGA firmware/PowerPC/Data Acq PC to optimize this transfer?
Thanks,
Ben
__________________________________________________________________
Ben Mazin Phone/Fax: 805-893-3344
Assistant Professor
Department of Physics
University of California Office: 2015A Broida Hall
Santa Barbara, CA 93106 USA http://www.physics.ucsb.edu/~bmazin/
