why the qnx pcm capture is not stability

I run qnx on the VMware.And the Sampling frequency of pcm capture is set to be 16000.The channel is 1.The fragsize is set to be 2048.Every time I request to read 2048 audio data.At this condition the time of every time select() should be 64ms.
But the problem is that the time of select()is not stability.Its time is “…30ms-94ms-30ms-94ms-30ms…”.
And I change the read size and fragsize.The result is same.one short time and one long time can be getted. there isnot a right time.

“I run qnx on the VMware”

“problem is that the time of sele() is not stablity … Why?”

The answer to the question is the first statement.

Thanks for your reply.The problem is solved.VMware is the reason of not stability.

More likely the underlying OS, MS Windows perhaps?