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ADSP-24169 : Execution times  slower than expected by a factor of 2

Question asked by SimonRizzello on Apr 30, 2010
Latest reply on May 13, 2010 by jeyanthi.jegadeesan

Hi there,


We're benchmarking the performance of the ADSP-24169 processor, and the results we get show that the DSP algorithm execution is slower than we were expecting.


To sive a specific example, we are running the FIR algorithm with 64 taps.


Running the FIR64 benchmark, the DSP should be executing 1 multiply-accumulate in SIMD mode, which means 2 taps per clock cycle. With 64 taps, this should take 32 clock cycles per output-sample. In addition, there should be a 1 clock-cycle int->float conversion on the input, and 1 clock-cycle float->int conversion on the output.


We operate on 1024 samples in a block, making 1024 x (32+2) = 34816 clock-cycles => 87 microseconds (assuming 400,000,000 clock cycles per second.)


However we measure an average execution time of 62257 clock cycles => 156 microseconds


I've attached our test application project, which when run will execute a test benchmarking this algorithm.


The benchmark is executed in the DspMain thread by function dofn.


Have you any suggestions as to what is causing the slow down?


Kind Regards,