Slow outputs analog on the cDAQ-9178

My control of the C language application calls the DAQmx API 200 times per second to update some AOs, using the following call:

DAQmxWriteAnalogF64 (taskHandle,

1, TRUE, 0.0, DAQmx_Val_GroupByScanNumber, data, NULL, NULL);

On a system with a single chassis cDAQ-9178 and two modules OR 9264 AO, it works correctly with a task of up to 4 channels. If I add channels to the AO job, the flow slows down below 200 Hz (5 ms). Here are the times:

Chans ms

8 6.8

16 13.4

32 26.9

How can I write 1 sample per channel, more than 32 channels, all 5 ms? It's a control application that meets the entries, so I can't write several samples per call.

Thank you.

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