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C6678 Performance Discrepancy Between "Benchmarks" and EVM Board

The Kidd
Prodigy 25 points
Other Parts Discussed in Thread: DS90LV028AH

Hi -

Super newbie here, so be kind  :).

In comparing the published benchmarks of DSPLIB routines (from ... dsplib_c66x_3_1_0_0/docs/DSPLib_c66xTest_Report.html) to the provided examples (  from dsplib_c66x_3_1_0_0/packages/ti/dsplib/src)  ... an example running on a TMDXEVM6678L doesn't even come close to the published results ... but I may be completely misunderstanding something.

For example, for the routine DSP_mat_mul:

  CYCLES (from Test_Report):   2/8*r1*c2*c1 + 22/8*r1*c2 + 38/8*c2 + 17

  Results from running the example from dsplib_c66x_3_1_0_0/packages/ti/dsplib/src/DSP_mat_mul:

[C66xx_1_0] DSP_mat_mul    Iter#: 1    Result Succesful (r_i)    R1 = 8    C1R2 = 8    C2 = 4    natC: 10860    intC: 4110
[C66xx_1_0] DSP_mat_mul    Iter#: 2    Result Succesful (r_i)    R1 = 8    C1R2 = 8    C2 = 8    natC: 21317    intC: 8123
[C66xx_1_0] DSP_mat_mul    Iter#: 3    Result Succesful (r_i)    R1 = 8    C1R2 = 8    C2 = 12    natC: 31813    intC: 12166
[C66xx_1_0] DSP_mat_mul    Iter#: 4    Result Succesful (r_i)    R1 = 8    C1R2 = 8    C2 = 16    natC: 42309    intC: 16209


The calculated # of cycles is about 20-30 times less than the measured.  I guess I assumed the published examples would be closer (I used the provided GEL file).

Suggestions?
 

    Ned A.

  • 0
    Prodigy 20 points
    I do not have a suggestion for you. Perhaps you can answer a question I have. I have a question regarding Texas Instruments DS90LV028AH High Temperature 3V LVDS Dual Differential Line Receiver. A 100 ohm input termination resistor is recommended in the specification. What are the effects if a termination resistor is not used? The input signal is either high or low representing a Built In Test function being either in the ON state or OFF state. Will not using a termination resistor cause any switching problems such as with noise?
  • 0 in reply to Ken Elmer
    Prodigy 25 points
    This seems like the wrong forum for such a question, but improperly terminated LVDS lines are vulnerable to noise, ringing, and excessive voltage (from the ringing). The recommendations should be followed (unless you have a highly controlled environment and you know such things won't occur).
  • 0
    TI__Mastermind 35645 points

    Hi,

    Thanks for your post.

    Ideally, the cycle count performance of DSP library routines should match with the test report of c66x DSP library but i wonder, you could also use CCS profile setup to calculate the number of exectuted instructions and number of CPU cycle counts and check with the performance benchmarks of test report of DSP library routines. For more info. on how to use the CCS profiler setup, you could see the below post to compute the CPU clock cycle count:

    https://e2e.ti.com/support/development_tools/code_composer_studio/f/81/t/114580

    Also, please cross check the the formulas used in the DSP lib. test report with  DSP library manuals for calculating reliable cycle count results which needs to be compared for.

    Kindly ensure to use the correct formula to calculate cycle count for big endian COFF/ELF format and little endian COFF/ELF format appropriately to compare the benchmarks results of your measured versus DSP library routine test report.

    Thanks & regards,

    Sivaraj K

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