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Adventurer
Adventurer
1,083 Views
Registered: ‎03-28-2014

Aurora 64/66 Efficiency

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According to PG074, the overhead associated with the Aurora 64/66 protocol is 3%, however in my testing I'm seeing closer to 6% overhead (or 94% efficiency).

 

For my test setup, I've got a 4 lane, 10.3125Gbps per lane interface looped back on itself using a QSFP loopback module. I hold tvalid high on the transmitting side until 34359738368 clocks of data have been transferred (transferred meaning tvalid=1 and tready=1). On the receiving end, I start a counter when I receive the first tValid signal and continue counting until I've received all of the transmitted data (34359738368 clocks of data). I'm using the streaming mode with no flow control.

 

I'm seeing that it takes 36635450132 clocks to transmit 34359738368 clocks worth of data, which works out to 93.7% efficiency.

 

What can I do to get to the advertised 97% efficiency?

 

1 Solution

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Xilinx Employee
Xilinx Employee
1,028 Views
Registered: ‎03-30-2016

Re: Aurora 64/66 Efficiency

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Hello @dcwhitehead

 

@digitate is correct that the encoding alone has  (66/64)-100%=3.125% overhead, so, 97% is not possible.

We do aware of this IP performance limitation, especially if customer is expecting to use all of Aurora IP bandwidth.

 

Current Aurora 64B66B IP will loss 4 cycles ( tready==low) every 66 cycles == 93.93 % efficiency.
So your calculation is very accurate.

We are planning to enhance this performance on the next Vivado 2018.3 release. (will be released .... soon)

Please increase the line rate of Aurora 64B66B IP for a work-around. This is your only option for now.

 

Thanks & regards

Leo

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6 Replies
Observer digitate
Observer
1,040 Views
Registered: ‎02-06-2018

Re: Aurora 64/66 Efficiency

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97% is not possible - the overhead due to 64b66b encoding alone is 3%. On top of that will be higher level framing, ie the Aurora protocol itself.

 

93.7% seems reasonable.

I have not used Aurora.

Xilinx Employee
Xilinx Employee
1,029 Views
Registered: ‎03-30-2016

Re: Aurora 64/66 Efficiency

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Hello @dcwhitehead

 

@digitate is correct that the encoding alone has  (66/64)-100%=3.125% overhead, so, 97% is not possible.

We do aware of this IP performance limitation, especially if customer is expecting to use all of Aurora IP bandwidth.

 

Current Aurora 64B66B IP will loss 4 cycles ( tready==low) every 66 cycles == 93.93 % efficiency.
So your calculation is very accurate.

We are planning to enhance this performance on the next Vivado 2018.3 release. (will be released .... soon)

Please increase the line rate of Aurora 64B66B IP for a work-around. This is your only option for now.

 

Thanks & regards

Leo

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Adventurer
Adventurer
1,023 Views
Registered: ‎03-28-2014

Re: Aurora 64/66 Efficiency

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@karnanl,

 

What kind of performance enhancement do you think we will see in Vivado 2018.3, specifically for the streaming configuration?

 

Thanks,

Dan

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Xilinx Employee
Xilinx Employee
1,012 Views
Registered: ‎03-30-2016

Re: Aurora 64/66 Efficiency

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Hello Dan @dcwhitehead

 

I am expecting 2 cycles loss every 66 cycles  (instead of 4 cycles loss).
If needed I can do simulation using 2018.3 nightly build to check the latest IP, but not until mid of next week.

 

Thanks & regards

Leo

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Adventurer
Adventurer
1,006 Views
Registered: ‎03-28-2014

Re: Aurora 64/66 Efficiency

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Leo,

Thanks for the info. Glad to hear it.
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Xilinx Employee
Xilinx Employee
916 Views
Registered: ‎03-30-2016

Re: Aurora 64/66 Efficiency

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Hello @dcwhitehead


Just confirmed the latest Aurora 64B66B IP using 2018.3 latest build.
I can confirmed that Aurora 64B66B for GTY has been updated.

In Streaming mode this IP loss 2 cycles every 66 cycles  (means 96.96% efficiency). See picture below.

 

Thanks & regards

Leo 

XF_AURORA_64B66B_STREAMING_CYCLE_LOSS.png
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