Methods and structure for enhanced SAS expander functionality to store and forward buffered information transmitted from a SATA end device to an STP initiator device while managing use of Non-Zero Offset (“NZO”) field values in DMA Setup FISs transmitted by the SATA end device. The enhanced expander establishes a connection between an STP initiator and a SATA end device. The expander forwards a read command from the initiator to the end device. If NZO use is supported and enabled in the end device, the end device may return read data in any order by use of the NZO field values in multiple DMA Setup FISs. The expander is further adapted to store received data and the associated multiple DMA Setup FISs from the end device in its buffer and forwards the stored data to the initiator device. In another embodiment, use of NZO in the end device is disabled.