Control of whether Programmed I/O is used instead of DMA for small packets:
0- no (use DMA)
1- use PIO for small packets if available (default)
1will fall back to DMA if PIO is not currently available.
2- use PIO for small packets and fail if PIO is not available.
2will fail to create the stack if the hardware supports PIO but PIO is not currently available.
On hardware that does not support PIO there is no difference between mode
1 and mode
In all cases, PIO will only be used for small packets (see EF_PIO_THRESHOLD) and if the VI's transmit queue is currently empty. If these conditions are not met DMA will be used, even in mode
2 will not prevent a stack from operating without PIO in the event that PIO allocation is originally successful but then fails after an adapter is rebooted or hotplugged while that stack exists.