4 ms·
> I'm a bit puzzled why the 8087 doesn't need the constant log2(1 + 2-1), which is used by that algorithm. Not necessarily. For example, the algorithm for 2^x
by atq2119 6y ago
> I'm a bit puzzled why the 8087 doesn't need the constant log2(1 + 2-1), which is used by that algorithm.
Not necessarily. For example, the algorithm for 2^x with x between 0 and 1 just has to subtract the largest value in the table from x and perform the corresponding shift-and-add on the result. So for large enough x, they may have just done shift-by-2-and-add multiple times on the result, subtracting the corresponding log multiple times from the operand.
Though that still leaves the question of why they left out this particular table value and not any others. It may have been a balancing act of overall accuracy and performance vs table size vs microcode complexity.