The Museum of HP Calculators

HP Forum Archive 09

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Death of RPN
Message #1 Posted by Tom (UK) on 16 Dec 2002, 7:27 a.m.

Some time ago an ex-employee of ACO said when thay closed them down that:

"Unfortunately, the Saturn is becoming obsolete this year, and nothing has been done to redisgn it"

All the current (and recent ex) RPN calcs had the operating system running on a Saturn processor. It doesn't take much imagination to see that when stocks run out HP will have nothing to run the RPN software on.

Hence HP is re-badging old calcs, or using AOS based chip sets.

The only chance to use all the good RPN routines is to hire some programmers to port it to another processor, or have an interpretor running on a faster processor (both difficult as the Saturn is a fairly unique bit of hardware)

The only other (minimal cost) option is to use the 11/15c roms in the 'new' 12c - you know, the one with the rubbish keyboard.

Other choices are to desing a new calc (remember the Xpander?) or have a good RPN calc on a PDA or using the 48/49..... but the chances of HP doing this are 1 in 10^42.

Buy those hp48's while you can...

(well thats my rant for this month)

Re: Death of RPN
Message #2 Posted by Vassilis Prevelakis on 16 Dec 2002, 9:38 a.m.,
in response to message #1 by Tom (UK)

You are confusing development with production. The intel 8051 is still being used even though decades have passed since the design was fixed. Many companies (e.g. Philips) have made minor extensions to the architecture, but the new designs are essentially compatible (or can be switched to a compatiblity mode) with the original 8051.

HP may continue to produde Saturns for as long as there is a demand for the calculators. If there is demand for a specific package (e.g. 12C) then you only need to improve manufacturing techniques (and lower production cost). HP may realize that for certain applications the technology has matured (e.g. ballpoint pens, people still buy expensive ones, not because they have more features, but because they look better, feel better and impress the owner's friends). I would guess that in the case of the 12C, users do not really want something better, what they have is what they need/want. Of course by making these calculators feel cheap HP is going to lose that market as well (its like Parker or Cross making their pens look like plastic BICs).

If you want to use another processor, you can just write an emulator for the saturn architecture. It has been done and the code is generally available. Why do you think that you need to port the source? Users do not care whether their calculator runs native code or emulated code. Saturn can become the p-system of calculators.

The BIG cost is tooling for the calculator itself: keyboard, covers, display etc. This is the limiting factor.

So I would agree with your suggestion that we will end up with a "virtual" calculator running on a PDA. I wouldn't like that, and I would try to hang on to my existing calculators as long as I can, but without replacements, the time will eventually come when I'll have to switch to a new platform.


Re: Death of RPN
Message #3 Posted by Tom (UK) on 16 Dec 2002, 12:44 p.m.,
in response to message #2 by Vassilis Prevelakis

My understanding is that the Saturn will soon die (end of production) as HP won't port it to an available semiconductor technology (1.2um or smaller). Porting to a smaller geometry (which is almost all that is available now, and 1.2um is getting scarce) would not be cheap and I don't see HP doing that. Hence I don't see production of any of the current RPN calcs lasting very long. HP have not rushed out true replacements for dropped calculators.

HP owns the code that we know and love as being fast and accurate and this runs on the Saturn processor that HP also own. I would love to see an emulator on some of the current fast processors, where have you seen this and what processors does it run on? - perhaps HP are working on this.

The 8051 design is still available because it has been ported to technology that is currently manufactured. Indeed our company has designed our own 8051 core to embed in our own designs, (we also have a DSP of our own design).

Does anyone know what technology the Saturn processor is in? I'd guess >>1.2um technology as it is not very fast (4MHz) by standards of even 5 years ago.

I don't wish production of 'proper' RPN calcs to end but the situation with the Saturn hardware is not good.

PS - My posting was listed as a bit of a rant - so my argument may be a bit leaky - thanks for your constructive critisism - it's made me realise perhaps we may have seen the last of the current crop but hopefully not the end of HP + RPN. However recent HP releases have been very disapointing.

Re: Death of RPN (Reports greatly exaggerated . . . )
Message #4 Posted by Paul Brogger on 16 Dec 2002, 10:19 a.m.,
in response to message #1 by Tom (UK)

The user interface aspects which implement RPN calculator behavior don't need to run at anything like processor speeds, so RPN may be implemented on any reasonably fast CPU, regardless of its architecture and instruction set.

As romantic as the notion of developing on proprietary components may seem, it just doesn't make business sense. Using industry-accepted components increases the talent pool available for development and support, simplifies training, and deepens the developers' toolboxes.

With regard to its RPN calculator offerings, HP hasn't made many decisions lately that I like, even though all of those decisions are presumably supported by something that passes for corporate wisdom. But I don't see how discontinuing the Saturn line will itself inevitably preclude the future offering of RPN calculators. (Maybe some developers would care to chime in here?)

I think there's still hope for a legitimate RPN interface. I most regret the ongoing decline in HP structural and appearance qualities. We've not seen the like of the made-in-America Pioneer models (one example) for many years, and are unlikely to ever see that level of care in calculator creation out of HP again.

Re: Death of RPN (Reports greatly exaggerated . . . )
Message #5 Posted by Chan Tran on 16 Dec 2002, 12:58 p.m.,
in response to message #4 by Paul Brogger

Just wondering, with all the spin off and merger does HP still have the semiconductor manufacturing capability to product the Saturn chip?

Saturn processors
Message #6 Posted by Randy Sloyer on 16 Dec 2002, 1:40 p.m.,
in response to message #5 by Chan Tran


You absolutely do not need a Saturn processor to do RPN. RPN was an elegant way to implement a mathematical interface in a limited capability first generation dedicated microchip product. The HP-35 was designed before general purpose microprocessor chips such as the 8008. It would have been much easier for the HP engineers to use an off the shelf micro from a firmware perspective, but the product would not have fared very well in the market due to the costs of the chip and power consumption. I this is why HP developed the Saturn in the first place - it is a low power, highly robust dedicated processor for a single application - calculators. It could be considered a general purpose micro, but it's architecture is optimized as HP saw fit.


To the best of my knowledge, the Saturn processor has never been manufactured by HP. Nippon Electric (NEC) has been the sole source of supply. HP designed the chip but did not have the CMOS process to manufacture. I don't think HP ever manufactured IC's of this complexity. I am probably wrong on this one, but wasn't opto-electronics their only silicon based products? - Now with the Agilent spin-off.

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