FPGA DMA FIFO Speeds Question

[otheredward]

Hello, I have a couple questions about FPGA DMA FIFO transfer rates. Specifically, if I have a R series board and create a Target to Host DMA FIFO how fast does information move from the FPGA to the computer memory? Is the limiting factor the bus speed, thus the PCIe bus speed is the transfer rate?

Also wondering, the FlexRIO boards as listed as having 16 DMA channels verses the 3 available on the R series boards. But the FlexRIO boards reside in the PXI chassis which has it's own memory and processor. Does this mean the FPGA has 16 DMA channels to the PXI chassis's memory or the computer's memory? How fast can information be transferred off the PXI chassis to the computer?

Thanks.

[Dave-C]

Hi Edward,

The speed of DMA FIFOs depends on many variables, and bus speed is one of those.  Since the communication is occurring over the PCIe bus, obviously it can't exceed that rate.  However, rates can also vary between different pieces of hardware, depending on which direction data is being sent, and bus traffic.  Is there a specific speed threshold that you're looking for?  Similarly, the PXI bus will play a role in the communication to a PXI target since that is the bus the communication happens over, and again, it will depend on the exact devices involved, direction of communication, etc.  FlexRIO is one of the fastest communicating devices that NI offers, however, depending on the needs you have.

Regards,

-Dave C