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Application Performance Comparison

 Optimizing the Ported Code 7

Methods based on almost all the new DSP56800E features, which are summarized in Section 1,

“Introduction,” were used to improve the speed of the application. Table 3 and Table 4 present the overall

results obtained after most of the time-consuming functions were optimized.

The program memory size decreased by 2 percent compared to the ported code, nearing the size of the

DSP56800 reference code. Better code density was achieved because more registers were used and some

instructions were replaced with more flexible ones. The data memory area slightly increased because of the

gaps introduced by alignment requirements.

Table 4 illustrates the speed improvements.

The DSP56800E optimization methods produced an increased speed of about 9 percent compared to the

ported version. The optimized version runs in less than half the number of cycles compared to the

DSP56800 reference version. Remember that the actual execution time is much shorter, since the

DSP56800E is a faster processor.

Table 5 indicates the effects of optimizing the most time-consuming functions. The results are presented

globally, not for each individual act of optimization.

Table 3. Size Comparison

Code

Program Memory

(Words)

Data Memory

(Words)

Constants/Tables Variables

DSP56800 reference 4735 1092 909

DSP56800E ported 4957 1092 909

DSP56800E optimized 4856 1100 911

Optimized vs. ported –2.04% +0.73% +0.22%

Optimized vs. reference +2.10% +0.73% +0.22%

Table 4. Speed Comparison

Data Component

or Mode

Code

Worst Case

(Cycles)

Processing Load

(MCPS)

Speedup Factor

Relative to Reference

Transmitter DSP56800 reference 1352 0.81 N/A

DSP56800E ported 571 0.34 2.37

DSP56800E optimized 498 0.30 2.71

Receiver DSP56800 reference 9870 5.92 N/A

DSP56800E ported 5154 3.09 1.91

DSP56800E optimized 4692 2.81 2.10

Full duplex DSP56800 reference 11222 6.73 N/A

DSP56800E ported 5697 3.43 1.97

DSP56800E optimized 5190 3.11 2.16

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