Let's clarify "Host" and "Target" here. Your myRIO is running a Real-Time operating system; that's considered the "Host." It also contains an FPGA; that's the "Target." If the myRIO supports it, you can also connect directly from the Windows machine to the FPGA, bypassing the Real-Time system, in which case the Windows computer is the "Host" and all FPGA communication between the host and target goes over Ethernet, which is a bit slower. I believe, but don't have a way to test or confirm, that you can still use a DMA FIFO on a remote FPGA target. However, if you are using the Real-Time portion of the myRIO, then the host-to-target DMA FIFO will transfer data from the Real-Time system to the FPGA, and you'll need some other way (such as TCP or UDP) to send data from the Windows computer to the myRIO.