42S reincarnation is possible?


I'm just wondering: is it possible to uploading 42S ROM into a HP17BII? Or 17BII ROM is replacable with 42S ROM if we changing their ROM-chip or uses a burned EPROM?

Edited: 31 Jan 2011, 9:22 a.m. after one or more responses were posted


It is not possible. The 17bII and 17bII+ do not have a flashable ROM or even a means of transferring data electronically into the unit. There is no I/O except for an infrared transmitter that only transmits data to an HP 82240B Printer.



Edited: 30 Jan 2011, 4:26 p.m.


The hardware/cpu in the 17bII+ is completely different. Wouldn't run even if you got it in there.



Yes. This too...


I have no data about types of CPU in the two unit, but on the finseth data base the two model seems to me same, with different ROM (the LCD, CPU (Lewis chip), memory, ... same).

I found an article here about the 42S:

I never opened a HP-42S, but from was I read in some posts, I think that there is a place for a second ROM. It's true for the HP17BII which have the same hardware, and it is how HP managed the two HP17BII versions (english and international with multiple languages): one common ROM and a second optionnal ROM.

I'm not a guru, but it's seems to me possible...



You are confused with two hardware types.

HP 17BII ( Pioneer ) = HP42S and ROM's can be swaped physically.

HP 17BII+ the golden or grey new series have nothing to do with the HP 42S as hardware is different and significantly worst.



I'm talking about HP42S and HP17BII.

About this:

And this:


...but, you're said, this is possible? Anothers said this is not possible!
I feel, because this two machine is SO similar.

1.) 42S ROM is available (many emulators uses this files)
2.) Which type of ROM in this machines?
3.) Burn an EPROM
4.) Solder that EPROM
5.) Enjoy your 42S with 17BII skin

Life is simple :) :P - as I think... :P

Edited: 31 Jan 2011, 9:18 a.m.


It's not Csaba that's confused. He stated from the beginning that he is talking about the 17bii. Others have assumed he meant 17bii+. However, he unfortunately used the word uploading, which caused some confusion on what he meant, I think. Now it seems clear he meant physically installing a new ROM chip after burning the 42s ROM onto it.


Yes, I'm usually in trouble with English...


Your English is fine. But your original question remains: can it be done?


Never forget: Your English is orders of magnitude better than our Hungarian! Anyway, I'm curious as well what will be the answer to your question.


I never assumed he was talking about the 17bII+. I just mentioned both so I could cover both bases.

Using a the traditional method of flashing the ROM via any method is not possible. The ROM is hard coded. This is the only situation my answer covered. I really didn't know that a replacement ROM could be installed in the 17BII. If it can, then a change is within the realm of possibility.

Unfortunately, you will have to either find a a 42S ROM laying around or you have to manufacture one. I don't know any individual who is capable of manufacturing ROMs. I am under the impression that it requires a lot of resources, which would be within the realm of a chip manufacturer.



Edited: 31 Jan 2011, 1:21 p.m.


I am out of school here, but nevertheless I am sure Csaba was talking about using an E(rasable)P(rogrammable)ROM, which is supposed to be DIY with a simple kit. So it would seem one would only need an EPROM of the right form factor, compatible energy demands, speed, etc., plus the 42s ROM code. Is this what you meant, Csaba?


Ahhh... That makes sense. I didn't even consider that possibility. That would be really cool if it can be done and works.



  1. The 42S operating system code is part of the processor die in the form of masked ROM.
  2. 42S OS ROM is 64 kb in size.
  3. The external ROM port is 8kb in size.
  4. The external rom is in a different address space than the OS.

If you need more reasons why it will not work, I might be able to think of some...


Looks like swapping boards is the easier way to go. Or just redesign a board from scratch. Kind of hardware Free42. ;)

Edited: 2 Feb 2011, 3:46 a.m.


However, it certainly wouldn't be too difficult to build some hardware around Thomas' Free42 and pay him some licence fee.

Anyway, it wouldn't sell well. For the educational market, HP is better off with the 35s, unfortunately.


May I remind you we did experience the fate of OpenRPN? Seems to be far easier to put some SW into existing HW than building some calculator HW for existing SW, at least that's what I have learned. And even the first isn't trivial.


Sure you're right, Walter. I was more thinking of HP to licence Free42, so I was offtopic in this thread :-(.


Speaking of the devil, I'm preparing to resurrect OpenRPN. I believe I finally have the necessary facilities to bring the project to fruition. However, this time I'm planning to take baby steps that lead to some dream calculators.


please do start a new thread outlining your plans?

i'd be keen to see an atmel ATMEGA1284P processor used: 128k flash, 16k ram, 4k eeprom, four 8-bit i/o ports. oh, and in a DIP package, meaning 0.1" pin spacing solderable onto veroboard by just about anyone.

quite literally, a complete hardware solution could be built onto veroboard, requiring just the 1284, a matrix of switches, a 16x2 off-the-shelf LCD module and a battery pack.


Walter is already on the right track. My current concept is to use existing hardware, such as the 35s, and replace the PCB. At the very least we end up with complete control and customization with the lowest possible overhead costs.


My current concept is to use existing hardware, such as the 35s, and replace the PCB.
Last time it was about taking a given PCB and put it into a new case, right? ;-)

However, if you manage to write a bugfree 35s-like firmware, you'd probably have some customers. If it's about changing keyboard lables, I personally would stay away from it. That's probably more difficult than just to have some cases produced in China - inluding paint job.

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