dma transfer stalling CPU

[jonster]

Hi,

We are using a PCI 6602 card for 3 dma sampling pulsewidth of 3 50kHz pulse trains.

This was implemented on a Intel Core2 quad cpu Q6700 @ 2.66GHz with 4GB RAM

and the computer had no problems with sampling this using a buffer of 10 samples. i.e. 3 pulse width dma sampling tasks with a 10 sample buffer.

Once we tried to port the program to another computer (Intel® Atom™ N270 1.6 GHz processor + 945GSE chipset 1 GB RAM) its CPU stalled. I event tried to set up 1 pulsewidth task using Measurement & Automation Explorer with a buffer size of 500 -> CPU rose to 80%, adding another task -> the first task was unable to read the buffer before it was overwritten.

Is there anyone that have had the same type of problem?

BR

Jonas

[Davidek]

Hi Jonas

Per definition DMA should not take CPU time, that's the whole point so that the DMA is the problem is unlikely. Are you using the PCI-6602 hardware with the other computer as well? I'm asking since the Atom processor is most common in laptops. What are you doing with the data you are collecting in your application? Do you do any analysis on it? I can only guess since I haven't seen you application but what I can imagine would happen is that you have a lot less processing capacity with the second computer and that the processing is taking too long, which means that the buffer is overwritten. If you don't have any analysis it could also be an issue with memory/CPU bandwith and how many DMA channels the chipset supports.

Best Regards

David

NISW

[jonster]

Thanks David,

For sure DMA should not hog my CPU that is why I was so supprised. I had created an empty application just fetching my data without any processing but without any difference. Even measurment and automation explorer stalled when a single task was set up. I'll investigate on your other suggestions though.

I'll post once I figuered out what caused the problem.

BR

Jongas