PCI-7813R R series DMA transfer speed

[SW-HW_Developer]

I would like to use for my data streaming application a PCI-7813R R series board.

Application requirement is 800Mbits/s peak speed, while PCI theorical speed should be 33.33 MHz × 32 bits = 1066Mbits/s / 8 bits = 133 MB/s.

I realized the speed test application in attachment and, running it on a PC that shares PCI bus between PCI-7813R and embedded video card, I only obtain a mean speed of 270Mbits/s.

Considering my application structure are my results reliable?

Are those performances within typical limits of PCI-7813R R series board?

thank you,

Marco.

[MarcoMar]

The above information was generated to test DMA throughput in one direction. In two directions the throughput changes. For example, the PXI-8170 with PXI-7811R might have 100 MB/s up and 37.5 MB/s down, but that is often decreased drastically for both when upload and download are done at the same time. 

This question depends on several variables. First it depends on what type of target that you are using. Determine if you are using a cRIO, PXI, or PXIe FPGA backplane or card. Second, it will depend on what RT Controller is being used to read/write the data on the host side. Finally, throughput will depend on the direction of the FIFO and whether there are multiple FIFO's involved. 

Here is a table created by R&D (Internal Wiki) that will give you a close approximation of DMA FIFO benchmarking for common Chassis and Backplanes:

Controller	Target	Target-Host	Host-Target
cRIO-900X	cRIO-9101	29	N/A
cRIO-901X	cRIO-9101	64	21
PXI-8170	PXI-7811R	100	37.5
PXI-8176	PXI-7811R	118	N/A
PXI-8170	PXI -7831R	64	37.5

[SW-HW_Developer]

My target is a PCI-7813R used on a standard PCI bus

The host machine is an Intel® Server Board S5000VSA equipped with 4GB of DDR2-533 ECC RAM and 2 Intel XEON CPU's (4M Cache, 3.20 GHz, 1066 MHz FSB) with a total of 8 threads

My test project has only one host to target DMA transfer active.

I would expect performances that are similar (or superior) to PXI-7811R with PXI-8170 controller

100MB/s=100*8 Mbits/s=800Mbits/s

am I wrong?

Is there something wrong in my test project?

Thank you,

Marco.

[MarcoMar]

Probably there are some bus limitations or the program you are using is not able to get the best from the DMA channel.

[SW-HW_Developer]

My speed test application is attached to this thread, could you help me by checking if it's getting the best from the DMA channel?

If you cannot check my application, do you have any benchmark application in order to get the best from the DMA channel?

How could I check if there's any bus limitation?

thank you,

Marco.