PCIe on Jetson TX2 - max. data rate

Hi everybody,

in the datasheet for the Jetson TX2 it says PCIe 1x4 is available with 5 Gb/s.
Is that the max. data rate in total or the data rate / lane - which would mean I could use it to stream 20 Gb/s in total?

Thanks for your support.

Regards,
Tom

To be more accurate, the PCIe v2 spec provides 5 GT/s (giga transfers/s) per lane. A GT/s is approximately the same as a gigabit (not byte).

There is of course an overhead with the encoding (8b/10b scheme for v1 and v2). Four lanes would provide 20GT/s, but this would in theory have an actual throughput of only about 80% of this…perhaps 16 gigabit theoretical throughput.

You may want to state what exactly it is that needs this transfer…it might lead to other solutions, e.g., compression schemes.

Hi,

thank you for your support. I feel more comfortable with your statement and we will probably test the transmission with a FPGA eval board.

Regards,
Tom

I would suggest that early on you check to see if the signal quality allows full PCIe v2 speeds (5GT/s). If signal quality drops it will fall back to v1 speeds (2.5GT/s). “sudo lspci -vvv”…where “LinkCap” is how fast the link reports it is allowed to go, and “LnkSta” is how fast the data lane is actually running. If it throttles back you’d have quite a mystery if you believe it is running in a mode that never happened.