Method and structure for performing floating point comparison

Details Method and structure for performing floating point comparison Method and structure for performing floating point comparison

1986-09-19

1989-08-15

Harkcom, Gary V.

Boots, shoes, and leggings

G06F 738

Patent

active

048581666

ABSTRACT:
Comparison of two floating point numbers is performed using a unique algorithm, which in one embodiment is implemented very efficiently in hardware, resulting in a very significant improvement in the floating point comparison execution time. In order to perform a floating point comparison, the exponents of the two numbers to be compared are subtracted. In many cases, the exponents are not equal, and simply determining which exponent is larger, combined with the signs of the mantissas of each of the floating point numbers being compared, is sufficient to determine which of the two floating point numbers being compared is larger. Alternatively, if the exponents of the two floating point numbers being compared are equal, the mantissas may be subtracted without need for shifting mantissas in order to equalize the exponents. In this manner, the floating point comparison operation is greatly simplified and the time consuming multiple shift operation is avoided, thereby vastly reducing the amount of time required to perform the floating point comparison, and thereby increasing the overall speed of operation of the microprocessor.

REFERENCES:
patent: 3814925 (1974-06-01), Spannagel
patent: 4229801 (1980-10-01), Whipple
patent: 4592006 (1986-05-01), Hagiwara et al.
patent: 4644490 (1987-02-01), Kobayashi et al.
patent: 4719589 (1988-01-01), Tanaka
Levine, "Fraction Addition or Subtraction or Comparison Overlap with Characteristic Comparison", IBM Tech. Discl. Bull., vol. 15, No. 7, Dec. 1972, pp. 2162.
Hayes, "Computer Architecture and Organization", McGraw-Hill Book Company, 1978, pp. 202-209.

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