daqmx performance, high cpu usage

[Kreuters]

hey

i have recently installed the latest DAQmx 8.5 on a laptop, along with a measurement studio application that acquires data using a 6062e daqcard. i checked the processor usage, and found it to be very high (~75%). to compare this i loaded up our old data acquisition app written in labview, and the processor usage was also very high, ~50%.

previously this application could acquire on the laptop using around 10% of the CPU. i have tried downgrading the DAQmx version, but ti seems to make no difference. to check i am not going mad, i checked the CPU usage when using the traditional NIDAQ drivers, and sure enough  the CPU use drops to about 10%.

can anyone explain this? i would like to get this fixed, it is badly affecting the battery life of the laptop.

thanks.

[Kreuters]

ok, to clarify, i downgraded to DAQmx 7.4 and checked the test panels in Max. Acquiring at 350k continuously used 40% of the cpu with DAQmx and 8% with the traditional drivers.

Upgrading to 8.5 causes the DAQmx test panel to use 60% of the CPU.

is this normal behaviour? is there any way to bring DAQmx processor usage in line with the traditional drivers?

[Kurt_NISalesEngineer]

Hi

Thanks for contacting National Instruments with your query. The following knowledgebase article might shed some light on this issue:

http://digital.ni.com/public.nsf/allkb/09D80223FA84113D86256D6A004B97C3?OpenDocument

Kind Regards,

Kirtesh Mistry
Applications Engineer
National Instruments UK & Ireland

[Kreuters]

that is of interest, but does not explain why i am getting such high cpu use with DAQmx 8.5 on one machine and not another of equal performance.

eg

Mac Mini 1.67 GHz CoreDuo chip can acquire from a simulated DAQmx device at 350kHz using ~8% of the processor
Laptop 1.6 Ghz Core2Duo chip can acquire from a simulated DAQmx device at 350kHz using ~20% of the processor

this is not plotting anything on the screen, just acquiring in the background. this is more than twice the CPU usage when you acquire using the traditional drivers, and when using an actual DAQ card the processor use jumps to ~50%.

there must be something causing this as we used to use old celeron 1.4 Ghz laptops with DAQmx and the processor usage was fine, under 30% generally.