The HP-12c and platinum Kinpo story

[dm319]

I started writing out a longish reply to this thread and realised it was best put into another post. I know we've heard the story many times that the 12c platinum is a rewrite-from-scratch, and I've seem people advise caution about buying the 12c platinum for exams where the exact answer is important. However, my TVM testing found something different. This was original reply:

(12-01-2024 01:50 PM)Steve Simpkin Wrote:  Perhaps. According to Wikipedia, the HP-12C Platinum is a complete reimagination of the HP-12C that was manufactured by Kinpo Electronics for HP. Unlike the HP-12C which, (more or less) run the same 1981 firmware on a real or emulated HP "NUT" processor, the HP-12C Platinum has completely rewritten software running on a 6502 processor core.,
https://en.wikipedia.org/wiki/HP-12C#HP_.../_Prestige
...
Additional information:
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https://www.hpcc.org/datafile/V22N3/platinum.pdf

(Apologies to those who've heard me say this already)

The forensic testing I did on TVM suggested to me that the software running on my 12c platinum did not come from a clean slate. Most of it is identical to Saturn-and-beyond era HP financial calculators, returning 12 digits, with presumably a 15 digit internal precision. I suspect it is running some of the same C code as those devices. However, there are two slight differences - one is that, unlike the Saturn TVM solvers, but like the 12c, it takes the ceiling of solve-for-N. Another difference is the solve-for-i behaves more like the regular 12c.

The article above is interesting, and I wonder whether the first device had these bugs, but they got fixed maybe? My device doesn't behave like described.

from the article Wrote:. For example, f CLEAR-FIN n=10 PV=100 PMT=-20, and
solve for i: it takes 15 seconds on the 12C and 40 seconds on the 12CP, but re-
solving for i only takes 4 seconds on the 12C since the existing i is used as an
initial guess; on the 12CP, it still takes 40 seconds, which implies that the solver
cannot take user-supplied initial guesses any more. This example is also useful to
show the occasional discrepancies in the results: solving for FV and setting the
display format to scientific notation (f ·) reveals a difference of 0.44%.

This takes 2 seconds on my 12c platinum and returns 15.09841448 compared to 15.09841448 on my 12c emulator.

While the platinum shows 10 digits, you can expose the 12 digit precision by subtracting what is visible, which shows that the actual result is 15.0984144771.

Just for fun I tried this on the rogue 12c. It returned 15.09841448 also. Using subtraction we can find the full result which is 15.09841447711221.

This isn't really a forensic test, because it should be a fairly easy solve-for-i, but none the less, the 12c platinum returns the same result to 10 digits as the 12c, but also returns another two digits. The rogue 12c returns an extra 6 digits over the 12c.

More digits can be nice, but only if they are good quality ones. Which one is the most accurate? Calculating a reference value in R, I could generate these accuracy measurements:

Code:

|calculator             | 1046_12cp|
|:----------------------|---------:|
|HP-12c                 |      8.54|
|HP-12c Platinum        |     10.90|
|HP-12c Rogue One       |     12.45|

The 12c platinum scores nearly 2 points more than the 12c, which means it does make good use of those two extra digits, in fact those 2 extra digits are correct. The Rogue 12c is more accurate, though not 6 digits more accurate.

And so the conclusion to this exercise is that the most accurate HP TVM solver for this question is, bizarrely, a device currently being pulled from the shelves, and the next most accurate is the 12c platinum, which is often derided for 'having different algorithms' to the regular 12c.

This solve-for-i isn't really a forensic test, but those tests do place the 12c platinum as some kind of meld of saturn financials and the old 12c.

The story of Kinpo completely reimplementing the 12c from scratch using a scanned user manual would fit more with the Rogue 12c IMO.

If anyone would like more information on why I think the 12c platinum is mostly a Saturn-era financial calculator, I can try to demonstrate why I think that (I hearing screaming into the distance of 'no please, not that again!').