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TMS320C6678: C6678, SRIO x1, x 2, x4 througthput

stephen li wai hung
Prodigy 60 points
Part Number: TMS320C6678

Hi all,

from the application notes,  when the payload size is less than 256 byte in 3.125Gbps/5Gbps, there is no difference in througthput. 

what is the dominant factors affect the througthput in small playload size?

www.ti.com/.../sprabk5b.pdf

And   C6678 could configured  1x 4 lane port, 2 x 2 lane port,  4 x 1 lane.

I wondering

if it is configured as 2 x  2 lane port, the trougthput   will be double of 1 x 4 lane port perfermance ?

if it is configured as 4 x 1 lane port, the trougthput will be four times  of  1 x 4 lane port?

please clarfiy .  

if not, what is the reason ?

Thanks. 

Stephen

  • 0
    TI__Guru**** 161600 points
    Hi Stephen,

    We're looking into this.

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    TI__Mastermind 43296 points
    Stephen,

    As noted in another thread you opened - e2e.ti.com/.../2478588 please refer to Throughput Performance Guide for C66x KeyStone Devices. With the small size of payload less than 256 bytes (maximum payload size of a RapidIO packet), the overhead from memcpy( ) in the driver may impact more to the throughput.
    /* Copy the received packet information. */
    memcpy ((void*)from, (void*)&ptr_sockData->addrInfo, sizeof(Srio_SockAddrInfo));

    >>if it is configured as 2 x 2 lane port, the trougthput will be double of 1 x 4 lane port perfermance ?
    >>if it is configured as 4 x 1 lane port, the trougthput will be four times of 1 x 4 lane port?
    Yes, theoretically it is. Some overhead e.g. memcpy, CPPI configuration, may slightly cause they are not exactly equal. You can find the data from the table 32/33 in SPRABK5A1.

    Regards,
    Garrett
  • 0 in reply to Garrett Ding
    Prodigy 60 points

    Hi,

    thanks for clarification .

    Acccoring to my understanding, in the following three configuration 

    config#1 's througth put should be double to Config#2 and config#3.

    Is it correct?

  • 0 in reply to stephen li wai hung
    TI__Mastermind 43296 points

    Stephen,

    Please refer to the section SRIO user guide 2.3.1.4 and table 2-4.

    The four SerDes lanes available on the TI SerDes module are configurable for various
    port widths as shown in Table 2-4. When configured to 1x mode, a port will consume
    1 transmit and 1 receive lane and run at the normal line rate specified through the
    serdes cfgpll, cfgtx, and cfgrx registers. Configuring a port for 2x mode will consume
    twice the amount of lanes and run at twice the speed, while a 4x configuration will tie
    all available lanes to a single port and run at 4 times the line rate.

    If your config#1 is 2 lanes with 2x mode each, and configure #2 is 1 lane with 2x mode, then yes config#1 's throughput is double to Config#2.

    If you config#3 is 1 lane with 4x mode, then its throughput is equal to config#1 and double to config#2.

    Regards,
    Garrett