The 4452 DSA device always uses an internal buffer in the PC. In LabVIEW, you call the AI Config.VI to reserve this memory space on your system. The board employs DMA (Direct Memory Access) to stream data directly to RAM without tying down the processor.
The 4452 does contain an on-board FIFO. However, this memory is just a temporary space for data before it is sent to the RAM buffer. This is totally transparent from the user standpoint.
