I'm running the latest NI-DAQ drivers (verion 7.4) on the PCI-6731 DAQ and after running for a while, my CPU usage raises to 100 % (actually, because I run on a 2 processor PC, the CPU usage goes to 50 %)
I'm using the NI-DAQ as a double buffer analog output in a Visual C++ 6.0 application.
I'm using the Config_DAQ_Event_Message to define a "half buffer empty" event. In this event I write 1 s second audio data at 8000 samples/s for 4 channels to the DAQ (32KB), using the WFM_DB_Transfer API. The normal CPU load will be < 1 %. But after while the CPU load increases to 100 %.
I also noticed that Task Manager shows me the following values:
"I/O Other Bytes" (See View - Select Columns...):
Normal operation: 400 Bytes/s
100% CPU Load: 400.000.000 Bytes/s !!!
So it seems that the 100% CPU load is caused by the amount of "I/O Other Bytes".
There is no place in my application that does 400.000.000 I/O operations / s, so I suspect that it must be somewhere in the NI-DAQ API or NI-DAQ device driver.
Is there some incompatibility with my PC ?:
PEAK 735 Multiprocessor system (2 x P4 3 GHz)
Windows XP Professional SP1
Paul