Difference of DMA and First Party DMA in SATA

DMA
The data is blindly transferred between the pre-programmed memory region, as described by the scatter/gather list.

First Party DMA
The mechanism is intended to allow the device to select the host memory buffer that is transfers data to or from.
The memory buffer selection mechanism is through the DMA Setup FIS.
IN the DMA Setup FIS, the Buffer ID field identifies the memory buffer.