Out of Memory Error, Buffer Sizes, and Loop Rates on RT and FPGA

Question

I'm attempting to use an FPGA to collect data and then transfer that data to a RT system via a FIFO DMA, and then stream it from my RT systeam over to my host PC. I have the basics working, but I'm having two problems...
The first is more of a nuisance. I keep receiving an Out of Memory error. This is a more recent development, but unfortunately I haven't been able to track down what is causing it and it seems to be independent of my FIFO sizes. While not my main concern, if someone was able to figure out why I would really appreciate it.
Second, I'm struggling with overflows. My FPGA is running on a 100 MHz clock and my RT system simply cannot seem to keep up. I'm really only looking at recording 4 seconds of data, but it seems that no matter what I do I can't escape the problem without making my FIFO size huge and running out of memory (this was before I always got the Out of Memory error). Is there some kind of tip or trick I'm missing? I know I can set my FPGA to a slower clock but the clock speed is an important aspect of my application.
I've attached a simplified version of my code that contains both problems. Thanks in advance for taking a look and helping me out, I appreciate any feedback!

Answer 1

David-A wrote:
The 7965 can't stream to a host controller faster than 800MB/s. If you need 1.6GB/s of streaming you'll need to get a 797x FPGA module.  
I believe the application calls for 1.6 GB over 4s, so 400 MB/s, which should be within the capabilities of the 7965.
I was going to say something similar about streaming over ethernet. I agree that it's going to be necessary to find a way to buffer most if not all of the data between the RT Target and the FPGA Target. There may be some benefit to starting to send data over the network, but the buffer on the host is still going to need to be quite large. Making use of the BRAMS and RAM on the 7965 is an interesting possibility.
As a more out there idea, what about replacing the disk in your 8133 with an SSD? I'm not entirely sure what kind of SATA connection is in the 8133, and you'd have to experiment to be sure, but I think 400 MB/s or close to that should be quite possible. You could write all the data to disk and then send it over the network from disk once the aquisiton is complete. http://digital.ni.com/public.nsf/allkb/F3090563C2FC9DC686256CCD007451A8 has some information on using SSDs with PXI Controllers.
Sebastian