64 bit driver

[submmAstronomer]

Hi,

I was wondering if a driver for the USRP would be released soon for 64 bit labview.  The memory limitation in 32 bit labview means that I am only able to stream ~1.5 seconds of time stream data to memory at 20 MSPS. 

Calculation:

I & Q, each double precision 8 bytes.  Total: 16 bytes/sample.

20 MSPS*16 bytes = 320 MB/second.

My computer has 24 GB of ram, so in principle I could easily stream >30 seconds of data.  However, 32 bit labview seems to want to allocate at most ~600 MB to an array and I can only stream < 2 seconds of data.  For my application, I need to be able to stream ~10 to 30 seconds of data at a time and then post-process with an FFT (requiring additional memory). 

Naively, releasing the same driver to support 64 bit Labview seems like it would just require a recompile but perhaps there is a lot more to it.

Cheers, Loren

[ErikL]

Hello Loren -

For the scinario you've described, our first recommendation would be to stream the data to disk and then retrieve it for post-processing.  We've done some benchmarking here and sustained >20 MS/s for > 1 hour.  One of the tactics we did use was to convert the Complex Doubles to interpolated I16's.  This reduces the data rate to about 2 bytes x 2 channels x 20MS/s = 80MB/s.  While my internal hard drive could not sustain that data rate, I was able to maintin it with a RAID array which took my disk write performance from 100 MB/s peak to a sustainable 600MB/s (and also boosted my storage capacity.)

We are planning a driver release with direct access to I16, eliminating the need to deal with Complex Doubles prior to writing to disk.

Support of a 64bit driver is on the long term roadmap. Requests such as this certainly help us prioritze going forward.

I have attached the Record and Playback VI I used in my own benchmarking.