Latency to send few data from uP to FPGA

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Latency to send few data from uP to FPGA

Postby tom78 »

Hello,

I am sending a small burst of data (32 Bytes) from the uP to the FPGA Virtex7 through PCIe GEN3 x8.
With an AMD processor, I see that the FPGA is receiving 1 TLP of 2x32bytes word (4 ns between each word, the first word has the address + 16 Bytes and the second only the last 16 Bytes).
With a XEON processor, I see 2 TLPs with a latency of 90 ns between them (the first TLPs has address+16 data and the second Address+16 data).

AMD processor is quite old (4 years) and XEON is very new.

Does someone know why I have this poor performances with XEON processor, and does I miss any FPGA IP configuration?

I am on LINUX and I use exactly the same driver for the 2 cases.

Thanks
tom78
 
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Re: Latency to send few data from uP to FPGA

Postby support »

Hello,

It's not clear what you mean with the uP sending bursts to the FPGA. As far as I know, there is no way to make an x86 processor send a burst of data, except completing a read request. Or is this what you did? Because if so, it's indeed quite possible different processors behaved differently.

Regards,
Eli
support
 
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