[USRP-users] Looking for ballpark figures on processor to USRP X310

Marcus Müller marcus.mueller at ettus.com
Mon Oct 12 12:41:42 EDT 2015


Hi Justin,

that question comes up pretty often. But: It's really something
extremely hard to tell.
200MS/s single channel /is a lot/. On the wire, you get 16bit per I and
Q, so that is 6.4Gbit/s; you can't even fit two of these through 10Gbit
ethernet.

For example, I've got a relatively new i7 4790K based workstation with a
10GE card sitting in a PCIe x16 slot. Getting 200MS/s into RAM is
definitely possible without much ado (you *will* have to adjust network
card settings so that interrupt coalescing is active), but doing
something useful with them at that rate is nearly impossible without
knowing extremely well how to optimize procressing. For example, I can
get a good 150MS/s if I let my graphics card render a 1024-FFT of every
1024-vector of samples, but even a highly optimized (hand-assembled SSSE
optimized) FIR filter with only very few taps runnning on my CPU cores
will not run in real time, leading to overruns.

So, the core question here is: what is it that you want to do with your
samples? If it's "storage in RAM for later processing", then you're fine
with fast desktop PCs, probably. Just make sure the PCIe slot you're
planning to use has enough PCIe lanes (in non-server hardware, you'll
usually only find PCIe x1 slots for "normal" cards (sound cards, 1Gbit
ethernet etc), and 16x for graphics cards, and often enough the second
graphics cards slot only has a 16-lane slot, but only four actually
wired lanes. Also, RAM can't be too much. Also, a recent OS would be a
good idea.

Best regards,
Marcus

On 10/12/2015 10:44 AM, Justin Powell via USRP-users wrote:
> Hi all,
>
> Looking to use the X310 and two SBX-120 daughterboards. I want to
> utilize the full bandwidth and pull in 200MSps of data on both ADC's.
> At 14-bits for each sample, that gives me 700MSps into the FPGA. The
> Kintex-7 chip on the X310 has 36MB BlockRAM.
>
> Anyone got experience/info on the processor they used to pull data off
> the FPGA? I've seen the FAQ where you use an i7 (+other specs I
> forget) PC but I wanted to see what anyone else's experience with this
> was?
>
> Cheers in advance.
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

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