Amazon is showing the price for the 35s reduced from $59.99 to $49.99 . Is there a better price out there somewhere?
Amazon's price for the 35s


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12282007, 10:32 PM
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12302007, 02:42 AM
Welcome back, Palmer! Did you happen to notice my post of 24 December, which revisited one of your archived posts? http://www.hpmuseum.org/cgisys/cgiwrap/hpmuseum/forum.cgi?read=130050#130050  KS ▼
12302007, 11:33 AM
Karl: I am in the process of catching up since I was distracted (actually, a lot more than distracted) by my wife's major surgery. I have taken a quick look at the commentary on the TI55II that you mentioned. It will take me some time to digest it thoroughly. However, I should note that you stated that
Quote: My recollection is that the TI55II displays eight digits but carries eleven digits internally. That would make sense with the problem described in your commentary where the mean is displayed as 6 but subtracting six from the displayed value yields 1 E10. Woerner Joerg's site lists the internal capability of the TI55II as eleven digits.
Palmer
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12302007, 04:13 PM
Hi again, Palmer  Happy holidays, and we all hope that your wife's surgery and recovery turns out for the best.
Quote: Yes, I'm sure that you're correct, and those three extra guard digits contain the small inaccuracy from recalculation of the mean. However, it's possible for those calculations to be exact if the data are entered in ascending or descending order: {4, 5, 6, 7, 8} or {8, 7, 6, 5, 4}. The only intermediate mean average of up to five input data that is not exactly representable using two or fewer decimal points, is the mean of three data having an odd sum.
On a TI55II or similar, try entering {4, 6, 7, 8, 5} using stat summation, or manually calculate I get 1E09 on my LED TI30, which also has an eightdigit mantissa and three guard digits. Reducing the possibility of overflow with an eightdigit mantissa was probably the reason for the TI55II's statisticalsummation methods. The guard digits were not to be considered reliable; on the LED TI30, they certainly weren't: http://www.hpmuseum.org/cgisys/cgiwrap/hpmuseum/archv016.cgi?read=107358#107358  KS
Edited: 31 Dec 2007, 2:33 a.m. ▼
12312007, 10:22 PM
Karl: The surgery was on the Friday before Christmas and my wife was home by Christmas morning. Now, there is a REAL Christmas present!
Quote: The ascending sequence is exactly the one that I described on V8N1P26 od TI PPC Notes and which yields an error of 1E10. For the descending sequence the error is +1E10. Either sequence yields exactly 6 on the TI55 which was the machine that the TI55II was supposed to replace. Both the TI55 and the TI55II use 11 digits internally and display 8. Neither one has the noncommutative multiply problem seen with the TI57, TI58 and TI59. However, there is something different going on in the mathematics of the two machines. For 2 divided by 3 the TI55 yields an internal value of 0.66666666667 while the TI55II yields a value of .66666666666. The TI55 yields similar rounding of the least significant internal digit for other simple tests while the T55II yields truncated results. I will try to dig out some more tests of rounding and report the results. I was surprised by the internal rounding in the T55 since I had thought that the TI95 was the first TI machine with such rounding. Are you aware of any specific test results of the accuracy of the multiplication algorithm of the TI30, TI55, TI55II, etc.? Palmer ▼
01012008, 01:23 AM
Palmer  Yes, good news indeed! Unfortunately, I have no insights to offer regarding accuracy and bugs of the legacy TI models, other than what I have already detailed with the original LED TI30  the first calc I owned in 1977, and for which I now have an identical replacement. That division result of the TI55II may be a symptom of the inaccuracies, though.  KS ▼
01032008, 09:45 PM
Karl: You wrote:
Quote:
Some linited testing shows that TI55 also provides rounding to the eleventh digit of the mantissa for multiplication. The TI55II does not round to the eleventh digit for multiplication but rather truncates. The TI30 truncates some of the time, but sometimes does something else. For example, for th product 2.222223 x 3.333333: Exact 13 digits 7.407409259259 If one emulates the statistics routine which finds the mean with the TI55II in user memory of the TI55 with the program R/S  RCL 1 = EXC 0 + 1 = EXC 0 x RCL 0 1/x + RCL 1 = STO 1 RST then after clearing memories 0 and 1 and pressing reset one can calculate by entering the values and pressing R/S. The machine will stop with the current mean in the display and ready for the next input. For the 4, 5, 6, 7, 8 sequence or it's reverse the mean will be exactly six. One can emulate the statistics routine in the user memory of the TI55II with the same routine but one does not need the leading R/S because with the TI55II the RST command returns the machine to program origin and stops.. For the 4, 5, 6, 7, 8 sequence the mean will not be exactly six but will be in error by 1E10. The change the response to a RST command caused unhappiness in the TI user community because it eliminated the capability to run iterative loops. That's a much worse "improvement" than changing the size or location of the ENTER key. Of course, that wasn't the major complaint since the TI55II and it's companion machines such as the BA55 and TI57LCD has the world's worst key bounce.
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01052008, 04:48 PM
Hi again, Palmer 
Quote: Yup, there were some math problems with the legacy TI30 and the TI55II. A summation "trick" for calculating very small quadraticequation discriminants with improved accuracy is given in the HP15C Advanced Functions Handbook. It allows A  BC to be calculated to 13digit extended precision. You had ported this method to other calculators, as described in one or more contributions to the HP Articles Forum. Here are  bonus!  three ways to obtain the three lowestorder decimal digits of the the exact 13digit product of complete operands using the 10digit HP15C, by exploiting its extendedprecision arithmetic to see "7409259259".
Statistical Summation Matrix Residual Matrix Multiplication The statisticalsummation method will also work on the predecessor HP34C and HP11C, with register R5 instead of register R7, and using "MANT" instead of "CLEAR PREFIX" on the HP34C.  KS
Edited: 6 Jan 2008, 12:58 a.m. after one or more responses were posted ▼
01052008, 07:19 PM
Quote:You mean quadraticequation discriminants, don't you? A somewhat more direct way to get an extra 3 digits on the HP48 and its relatives is: [ 2.222223 1. ] [ 3.333333 7.0474 ] DOT But the 15form rounding isn't always round to even. It's different for 15form multiplication than for 15form addition, so the extra digits may not be properly rounded to even. I wonder what the HP15 does with the extended products and sums? ▼
01052008, 07:51 PM
Quote: Oops! Yes, I did. My post is corrected.
Quote: You mean, 7.4074, don't you? (Gotcha!)
Quote: Uses each of them for calculating the final result, which is rounded to 10 significant digits for storage in the stack register or numbered register (unless I'm not understanding the question).  KS
Edited: 6 Jan 2008, 12:29 a.m. after one or more responses were posted ▼
01052008, 08:42 PM
Quote:Rounded how, was what I was asking. Rounded to even, or just truncated? There was a thread a few years ago on comp.sys.hp48 about this. The 15form arithmetic on the later Saturn machines isn't rounded to even. It wasn't rounded to even on the HP71 either, but for some reason, they did it differently on the HP48 than they did on the HP71. ▼
01052008, 10:04 PM
Quote: It seems that you're wondering whether the 13digit extendedprecision results are simply truncated (i.e., all digits correct in their places), or are rounded with or without bias (e.g, "to even, to odd, always up or always down"). In order for for the "correct" rounding to be always known, it would seem that additional digits beyond the 13th must be computed. I'm not sure if that is even done. However, I did check out the rounding of a 13digit internal result to the final 10digit result. The HP15C appears to round the 10th significant digit up to the digit of greater magnitude. So, the issue of any bias in the 13th digit would seem of minimal importance.
FIX 9 etc...  KS
Edited: 6 Jan 2008, 7:41 p.m.
12302007, 09:06 PM
The NewEgg newsletter, which you have to subscribe to, has a special until Jan 2. $51.99 with free shipping and no tax to some states (like mine). I was hoping to get one for Christmas but, alas, nothing. First time in 30 years I was disappointed to not get a Christmas present I really wanted. 