*Note.** This section contains data that is so
antiquated that we’re not sure it has much relevance
to modern hardware configurations. It is included for
the sake of completeness and as a historical curiosity
*.

With 80387 | No 80387 | |||
---|---|---|---|---|

Repetitions | Average | Repetitions | Average | |

2,000k | Time | 200k | Time | |

Operation | (seconds) | ($\mu$sec) | (seconds) | ($\mu$sec) |

Add | 25.9 | 13.0 | 34.3 | 172 |

Subtract | 25.9 | 13.0 | 35.3 | 177 |

Multiply | 28.4 | 14.2 | 44.3 | 222 |

Divide | 33.6 | 16.8 | 50.9 | 255 |

Inner
product ^{1} |
40.3 | 20.2 | 61.9 | 310 |

Scalar
multiply ^{2} |
30.2 | 15.1 | 45.0 | 225 |

Loop overhead | 1.3 | 1.3 |

^{1} sum += a[cursor[i]]*y[cursor[j]]

^{2} a[cursor[i]] *= scalar

A variety of floating point operations were monitored under MS DOS version 3.30 on a 16 Mhz IBM PS/2 Model 70 with a 16 Mhz 80387 coprocessor and a 27 msec, 60 Mbyte fixed disk drive. The 32 bit operations available on the 80386 were not used. Table 2 catalogs the time requirements of the simple arithmetical operations, inner product accumulation, and multiplying a vector by a scalar. All benchmarks were performed using double precision real numbers. The test contains a loop that was restarted after every 500 operations, e.g. 200k repetitions also includes the overhead of starting and stopping a loop 400 times. With this testing scheme, all loop counters and array indices were maintained in the registers.

The measurements in Table 3 provide a similar analysis of math functions in the Microsoft C Version 5.1 math library. These benchmarks were conducted with a single loop whose counter was a long integer.

With 80387 | No 80387 | |||
---|---|---|---|---|

Repetitions | Average | Repetitions | Average | |

300k | Time | 10k | Time | |

Operation | (seconds) | ($\mu$sec) | (seconds) | ($\mu$sec) |

acos | 36.2 | 121 | 30.5 | 3,050 |

asin | 35.1 | 117 | 29.9 | 2,990 |

atan | 26.0 | 87 | 23.0 | 2,300 |

cos | 37.7 | 126 | 25.3 | 2,530 |

sin | 37.0 | 123 | 24.7 | 2,470 |

tan | 31.7 | 106 | 19.2 | 1,920 |

log | 25.4 | 85 | 18.5 | 1,850 |

sqrt | 16.5 | 55 | 5.7 | 570 |

pow | 51.4 | 171 | 38.6 | 3,860 |

j0
^{1} |
235.1 | 784 | 60.7 | 6,070 |

j6 |
662.0^{2} |
2,207 | 176.3 | 17,603 |

y0
^{3} |
510.0^{2} |
1,700 | 146.4 | 14,640 |

Loop overhead | 3 | 3 |

^{1} Bessel function of the first
kind, order 0.

^{2} Extrapolated from 30,000
repetitions.

^{3} Bessel function of the second
kind, order 0.

Differences in loop overheads found in Table 2 and Table 3 are accounted for by the differences in the loop counter implementation described above. The 3 $\mu$sec overhead reflects the time required to increment a long integer and monitor the termination condition (which also involved a long integer comparison). The 1.3 $\mu$sec overhead reflects the time required to increment a register and monitor the termination condition (which involved a register comparison).