jeff@oakhill.sps.mot.com (Jeff Enderwick) (06/22/91)
I'm looking at an old i860 manual, sections 9.2 and 9.3. It appears that they propose fp division via reciprocal approximation and multiplication. The manual states that "Worst case error is about two least-significant bits", for both SP and DP. I've tried doing some error analysis, and I can't figure out how they came up with a maximum error figure that small. Does anyone know how to show this result, or does anyone know the number for the i860 applications group ? Jeff Enderwick jeff@otis.sps.mot.com
alan@saturn.cs.swin.OZ.AU (Alan Christiansen) (06/24/91)
jeff@oakhill.sps.mot.com (Jeff Enderwick) writes: > I'm looking at an old i860 manual, sections 9.2 and 9.3. It appears > that they propose fp division via reciprocal approximation and > multiplication. The manual states that "Worst case error is about > two least-significant bits", for both SP and DP. I've tried doing > some error analysis, and I can't figure out how they came up with > a maximum error figure that small. > Does anyone know how to show this result, or does anyone know the > number for the i860 applications group ? I have not seen the i860 manual you are referring too. I have however seen Motorollas dsp96002 manual and they perform division in a similar way. Using an initial approximation of 1/x then progressive improvement of this accuracy. eventually y/x is found by multiplying an accurate version of 1/x times y. If this is what you are referring too I can explain how the improved accuracy occurs. Alan > Jeff Enderwick > jeff@otis.sps.mot.com