Texas developed a RPN calculator in 1970's


The RPN logic, widely employed in the Hewlett-Packard (HP)
calculators, were about to be adopted by Texas Instruments, the
main HP rival in the calculator market. The Texas project have been
kept in secret since 1970's, until recently discovered.

Some TI-51 VI calculator prototypes have been manufactured, working
in RPN logic, and featuring the typical dual-width ENTER key,
normally found in HP machines. The TI-51 VI is a version of the
algebraic-logic model TI-51 III.

According to rumours, Texas Instruments were forced to abandon the
project, otherwise they'll need to pay royalties to Johann
Luckewicz, grand-grandson of Jan Luckewicz, the creator of RPN
logic. Such royalties are estimated to reach an amount of many
billion dollars. HP is supposed to succesfully negotiate a
perpetual license trade from Johann Luckewicz, while he was drunk.
Because this license, HP is the only manufacturer authorized to use
RPN system.

After founding the legal issue, Texas readily cancelled the RPN
project, and commanded the destruction of all prototypes and
associated documents, aware of juridical demands. Extra-official
informers referred a secret agreement, involving Luckewicz-grand-
grandson (sober), Texas and HP, to keep the market under monopoly.

Texas Instruments and Hewlett-Packard, both USA companies, are the
main scientific calculator manufacturers, since the first portable
models were developed. A Japanese committee, leaded by Casio and
Sharp, declared its intention to accuse HP and Texas to
International Chamber of Commerce, alleging monopoly of RPN system
and abusive trust, respectively. Texas and HP CEOs refused to talk
about the Japanese inquiry.

This picture shows a very rare TI-51 VI unit. It belongs to a
former Texas R&D engineer, which succesfully hid and kept the
calculator when he moved to Lirpa Labs. This unit is supposed to be
the last TI-51 VI still intact. Its collectible value is

Link TI-51 RPN !!!



This post comes exactly four months and one day early, I'm afraid ;-)

Greetings, Max


But it must be true - after all, it is on the Internet, right? ;^)


Lirpa Labs must be run by that guy Loof Lirpa who posts on the net a lot.


Jan Łukasiewicz is the guy's name, show some respect mate :-)


gileno --

Another clue is the numerous mistakes of English in the description you copied and pasted. I saw no indication that you knew the conceptual "TI-51-VI" to be fictitious. Unless, of course, you uploaded your own handiwork, which leads me to my next point:

The "esnips.com" site hosting the hoax TI-51-VI image also links to an adware server that Spyware Doctor categorizes as a "known bad site".

Good photos of an "undoctored" TI-51-III are at this site:


and this one:


-- KS

Edited: 30 Nov 2008, 9:38 p.m.


Agreed. The poor English usage leads me to question the credibility of the original posting (not this poster, but the one that this post was copied from). In addition, if you look at the picture, there is one glaring weirdnesses:

- Has only an x<>y function, but no Roll Down function

At a minimum, you'd need to have a Roll Up/Down key on there, or else much of the stack is unreachable. Either that's a huge flaw in the original calculator design, it's a two level stack, or the faker didn't think of that.

Scammers. ;-)



The RPN module for the TI-59 is well-known, so why not?

What is much less known is the AOS Emulator ROM for the HP41C that fully emulated, in every details, the TI59. It was described in detail by Joe Horn in a PPC Journal, see here: v11n9p20.
I was told that this module is ultra-rare and some collectors would give a fortune for it...

BTW, this issue of the PPC-J is particularly interesting, with a paper on the HP41 Forth, and an other on a new language proposal for the HP41 (called intermediate code) that was unfortunatly never implemented (afaik).



Hello J-F,

Unfortunately the link you provided doesn´t seem to work. Is there any alternative one?



Unfortunately the link you provided doesn´t seem to work. Is there any alternative one?
Maybe it was down right when you tried? I looked at it two different times with no problem.

:D Very nice little article (the link works here as well). Just *a little bit* exaggerated about INV ...


My history is TI-ish. I started with the pre-AOS SR-51A (no parentheses, just *,/,yx before +,-). But I always liked the INV key. It's simply intuitive. OK, I never imagined what would happen if I try INV =.

If you compare INV to a second generic shift key, INV has the advantage of creating a less cluttered keyboard. OTH, the generic solution is more flexible.


Yes, I discovered this article several years ago in the PPC CD-ROM set. I thought to make a April joke with it, but this thread was the opportunity too.

This shows that hoaxes existed before the internet-era, and this is also is a testimony of the little consideration of HP users of the time for the TI machines.


Edited: 3 Dec 2008, 2:53 p.m.


Obviously this is a hoax. MOSTEK and National Semiconductor manufactured RPN chipsets as well, and to my knowledge, they neither have paid billions nor have been sued for billions.


Considering that RPN was invented in the 1920s, any patents on it (and I doubt one could patent a notation back then) would have expired by the time the first HP calculator was released.


Considering that RPN was invented in the 1920s
Wasn't PN invented then, and reversed later?


I'd think so as well. RPN strongly relates to registers being used, aka "easier to implement in electronics and mechanics" - but for paper&pen calculations, the original PN is probably easier to use (well, is it? I never tried that <g>). So I'd assume that RPN was "invented", when electronic calculators were invented. I think the Friden 130 was the first to use RPN - certainly they did patent a lot of their calculator, but I'm not sure if RPN as a derivative of PN would survive a patent trial.


There's a couple of ideas where RPN came from. See Charles Hamblin1 or Charles Hamblin2. I bet that Hamblin would have gladly given credit to Jan Lukasiewicz
I don't think there's ever been any way to patent RPN or any logic system. However; that wouldn't preclude some scum sucking lawyer from suing so his victim has to give him money to go away.
The enter key on the TI 51 VI picture is different than the other keys. That could mean that it's a fake or that it was a one off thing. Maybe Joerg knows something about this, but if TI couldn't make a go of RPN, he may not admit it to us.


but if TI couldn't make a go of RPN

I don't think it really matters if TI ever experimented with RPN. They got the education market while HP got RPN. I bet HP would trade in a New York minute!

Possibly Related Threads...
Thread Author Replies Views Last Post
  [PRIME] RPN: another attempt at returning more than one value to the RPN stack Marcus von Cube, Germany 5 1,105 11-05-2013, 02:44 AM
Last Post: Marcus von Cube, Germany
  Another non-HP RPN vintage calculator joins the collection Michael de Estrada 2 889 07-23-2013, 04:10 PM
Last Post: Walter B
  OT: RPN calculator/dmm by ESI Kees van der Sanden 2 756 05-25-2013, 01:38 PM
Last Post: Kees van der Sanden
  "HP RPN Calculator Users" group on LinkedIn Philippe Lasnier 6 1,097 04-27-2013, 03:27 AM
Last Post: BruceH
  The next Texas Instruments graphing calculator ! Mic 10 1,300 11-16-2012, 08:47 PM
Last Post: bluesun08
  Texas Instruments TI-83 Plus review robertoataulfo 82 5,838 04-02-2012, 05:32 PM
Last Post: Antonio Petri (UK)
  OT: RPN calculator for Garmin GPS hpnut 3 637 03-22-2012, 08:44 AM
Last Post: Andrés C. Rodríguez (Argentina)
  The smallest ever LED RPN calculator Michael de Estrada 11 1,411 02-16-2012, 10:24 PM
Last Post: Bill Wiese
  [OT] Texas TI-88 robertoataulfo 7 1,118 01-07-2012, 05:26 PM
Last Post: Joerg Woerner
  Wang 360 RPN calculator aj04062 8 1,188 11-07-2011, 08:20 PM
Last Post: aj04062

Forum Jump: