Accuracy of Woodstocks  Printable Version + HP Forums (https://archived.hpcalc.org/museumforum) + Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum1.html) + Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum2.html) + Thread: Accuracy of Woodstocks (/thread215397.html) 
Accuracy of Woodstocks  Matt Agajanian  03242012 Hello all.
What are the accuracy, algorithm and computational improvements of the Woodstock series over the 35 and 45?
Re: Accuracy of Woodstocks  David Hayden  03242012 Check the "Technology" section at the bottom of the entry for the calculators on this web site. You'll find information on the technology used for the various models.
Re: Accuracy of Woodstocks  Matt Agajanian  03252012 Thanks for the compass point.
Re: Accuracy of Woodstocks  Eric Smith  03252012 The "early" Woodstocks (21, 22, 25, 25C) have only slightly improved accuracy over the Classics. The biggest improvements in the math algorithms are the ones found in the 27, 19C/29C, and 67/97. I'm not sure whether the 91 and 92 use these algorithms or the older ones. Some minor further improvements were made in the 30series, 41, and 10series, all of which use essentially the same algorithms.
The math algorithms got a rewrite for the 71B computer using Saturn, to be compliant with the IEEE 854 radixindependent floating point standard. These routines, minus some of the IEEE features, were used in all of the Saturnbased or Saturnemulating calculators (clamshell, Pioneer, and graphing).
Re: Accuracy of Woodstocks  Paul Berger (Canada)  03252012 While the 71B was designed to be complaint with IEEE floating point the math routines may predate it by a little bit, it would seem that I get the same results on a 75 or 85 as I do on a 71 so it would seem likely that they are using the same algorithims. The other thing that would contribute to this is the internal representation of floating point numbers has the same precision on the capricorn and saturn processors. Both use 64 bit registers internally for holding floating point numbers, the only difference is the placement of the sign in the register. The author of the BASIC section of the HP Journal article about the 85 says:
"High accuracy has been obtained for the HP85 mathematical functions by using essentially those algorithmsdeveloped first for the HP67/97 and subsequently improved for the HP32E, the HP34C, and the HP41C as discussed in previous articles.1"5 These algorithms are adjusted for the larger HP85 word size to retain accuracy. Real number calculations in the HP85 are performed in ternally to fifteen significant decimal digits and rounded to twelve digits for presentation to the user."
Re: Accuracy of Woodstocks  Eric Smith  03252012 The Capricorn architecture used for the Series80 and 75 is totally different than the Saturn architecture used in the 71B and later, with Saturn clearly being an evolution from the Nut architecture of the 41C. Study of the 71B code makes it apparent that it was an evolution of the code from the 41C, and the use of the same word length notwithstanding, it has no obvious heritage from the Capricorn code.
Re: Accuracy of Woodstocks  Paul Berger (Canada)  03252012 I am quite aware of the difference in architecture of the two processors, however that does not preclude them using the same algorithms. I will admit I am not a professional programmer however it seems to me that the concept of an algorithm is independent of Re: Accuracy of Woodstocks  Eric Smith  03252012 Sure, but the common base is the algorithms that originated in the HP35, and evolved through the 67, 30series, and 41C. The 75/Series80 doesn't appear to have influenced the Saturn routines in any significant way. The fact that they ended up with the same precision is more a matter of that they both happened to have a 64bit word, and not because one is a derivative of the other.
