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HP41 rom versions - Printable Version

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HP41 rom versions - Erik-M - 08-12-2020 08:40 AM

I just scored a nice HP41C tall keys made in USA calc with rom version GFF according the seller.
It will arrive from Germany next week hopefully, depending on the Chinese virus situation.
I am curious how to check the rom version of an HP41 and also which versions are in circulation, is it possible without service module ?
Which bugs has my version, I hope all of them :-).


RE: HP41 rom versions - AndiGer - 08-12-2020 02:51 PM

You can find a nice collection on ROM versions and bugs at Jürgen Keller's site

RE: HP41 rom versions - hth - 08-12-2020 04:02 PM

GFF is a quite common version that is very similar to HFF, only two minor changes were made in HFF.

HFF allows back-arrow-ON to break an infinite loop at power on with a zero length buffer and there is a minor correction to ROM function lookup with duplicate XROM that is unlikely to occur in normal use.

Tall key calculators do not have GFF from factory. It is possible to check the version without a service module. There was a sequence published long ago in some PPC journal that (probably) relies on some synthetic programming.

RE: HP41 rom versions - Didier Lachieze - 08-12-2020 06:35 PM

(08-12-2020 04:02 PM)hth Wrote:  It is possible to check the version without a service module. There was a sequence published long ago in some PPC journal that (probably) relies on some synthetic programming.

There are some instructions here.

RE: HP41 rom versions - Erik-M - 08-13-2020 07:05 AM

Thanks for all the info, I found some posts about roms but not the ones mentioned here.
The production year of this calc is 1980 so I guess it must be one of the last tall key versions, the GFF rom matches with the year/version list.
I assume a version with DDE rom is the most rare thing to find.


RE: HP41 rom versions - hth - 08-13-2020 05:52 PM

The DDD is the most rare thing known to exist. Smile

I said that GFF machines have slanted keys, as I would assume HP used up they tall keys and switched ROMs in tandem, so to speak. I met machines with slanted keys that are earlier than GFF, so my guess was that it will probably not exist.

However, when thinking about it again, my old CV with slanted keys and GFF was made just weeks earlier of another CV that has tall keys, so if they mixed and matched a bit a they factory (factories?) it is possible that GFF tall keys do exist.

To complicate things, machines were repaired back in the days and mine was no exception, it was serviced two times in its early existence. Still going strong after the last repair around 82/83 by the way, now it is a 41CL and my most used machine again.

RE: HP41 rom versions - Erik-M - 08-13-2020 06:38 PM

Yes I found some info on the DDD rom on Jurgens site, good info there.
I guess there is only one in known existence, what a find.
The one I bought is a USA model so maybe that also matters for the rom version.

Of course there are also reassembled ones but most of time its obvious, there is a 1986 CX back and a 41C tall key front on sale now, clearly stated as for parts so no problem but its an impossible combination.
My 11C has a 16C back, received it for free and have no idea how this happened :-)
There seems however to be a real 41CV tall key in existence but I never saw one.

Now I have to wait for this thing to arrive.

RE: HP41 rom versions - CY-CL - 08-14-2020 10:12 AM

Hi Erik

Here some pictures from a real TallKey CV.

The S/N is 2103 A 10255

This is the lowest know to exist real HP-41CV S/N.

Note: All CV’s in 1981 starts with a 1, also 10255. If you find a lower S/N which starts with a 0 then the backside comes from a HP-41C.

Actually two CV’s with TallKey are known to exist, the other machine has the S/N 10260. Both are manufactured in USA.


[Image: 01.jpg]

[Image: 02.jpg]

[Image: 03.jpg]

RE: HP41 rom versions - Erik-M - 08-14-2020 04:56 PM


Thanks for sharing the pictures, so it really exists, what a nice thing to own.
I started collecting about a year ago, I have my personal 41C from the 80s that I still use very often but I decided I want to have all models.
I guessed with 6 different ones I could complete my collection, how wrong I was :-)
The 41C tall keys was a nice find, not cheap but in good condition, lets see what I will find in the future, I don't want to pay crazy prices so I have to patient.