HP41 ROM module versions: anyone?


Hi, all HP41 users and addicts! ;-)

Just to add a time reference: do you remember this?

Those of you who deal with ROM images (MLDL, Clonix and related stuff) know that there are different versions for the same application/program set. I am trying to locate and store these different versions with the sole purpose of studying and learning (35YO+ technology and still going!). I have some different versions of some common ROM images and I still need to download a few ones (stored in actual hardware), but there are some 'gaps' in some version sequences I do not know if were filled with actual, commercial versions or if they never left the labs. There is also the OS ROM versions, and based on what I saw, each of the three basic ROM has its own version flag, which leads to another question (coconut related): is there any information regarding compatibility and/or restrictions or these three OS 'packs' (one IC each) can live together in any possible combination?

Because Meindert´s MLDL2000 has room enough to store up to 253 4K-word ROM images (FLASH ROM), I think most of these images may find their place over there at the same time. I checked TOS and found only one version of most available ROM (did not check all of them), but it does not mean it is the only one stored there. I will send an e-mail to TOS webmaster and ask about this.

Most of us here know of one single place where many HP41 ROM modules found shelter, but this particular source is void, no ROM image will be disclosed from there. Anyway, I believe that the ones that were lucky enough being out here are in hands that might be interested on sharing such data base, mostly because it is 35YO and will serve no commercial purpose. As an example, I have a working Extended IO module with a checksum value that does not match, but I also have a ROM image of another Extended IO, same version, with a valid checksum value. Well, it is somehow easy to change the checksum value, but what if the ROM contents are actually faulty? Only with another version or an original blueprint to check for possible errors.

We surely know that the MoHPC is not the place to exchange ROM images because of also very well known reasons, and I (as all of you, I guess) completely agree with Dave´s thoughts about that. Some of the ROM images I have stored here with me were downloaded from actual hardware, but I also happen to have ROM images I downloaded from the www. I took into consideration that if they are publicly available, chances are that they are public. So, if anyone wants to share this sort of information in an off-line fashion, I'd also gladly share the ROM images I have. Please, use the following e-mail address:

lc_vieira (aT) QUANTICA punto Com [dot] br

In time: I had some issues trying to download a card reader ROM image by using a NoVRAM and a MLDL2000 and did not get the results I wanted to. Because of evident physical issues, I used the NoVRAM to capture the card reader ROM image first, then I tried to copy it to a single SRAM block in the MLDL2000, but somehow the card reader image disturbed the HP41 operation. I happen to have 1E ROM version already stored (the one with that interesting bug already mentioned here some years ago), but I want to keep a copy of the 1G version. Anyone wishing to discuss this as well?


Luiz (Brazil)

Edited: 19 Nov 2009, 6:36 a.m.


Hi Luiz, quite a complex subject you raise here... I have enough problems keeping track of the revision for the few modules I have done, so let alone getting into the vast universe!

Seriously though, this is quite a daunting activity. And which one is that site you refer to as the "shelter of all ROM modules"? Not sure I follow that either. Do you mean those copies each one of us has got along the years? If so, we can contribute them to a 'central library' but who'll be the "librarian"?

Sorry, more questions than answers...

Edited: 19 Nov 2009, 9:54 a.m.


Ola, Ángel; ¿que tal?

I agree with you that it would be somehow an extensive, time-consuming activity, but I think it’s worth gathering all of these images together. At least the ones with common interest from known sources that have already disclosed such information so there is no copyright infringement. I already have my homepage but it needs both completion and refinement, as you can see. It is mainly intended to be used by my students, but I’ll get it finished and enlarged soon. I see no problems holding either the images or links to the publicly available ROM, provided that it is not an infringement.


Luiz (Brazil)

Edited: 19 Nov 2009, 11:51 a.m.


Hi Luiz, Ángel,

Rom images have been of my concern since I started my first Clonix development and I keep a nice bunch of'em some of which (the most common) are bundled with the Clonix/NoV software for the users to play with.

The ROM pacs listing from M. Wherli at www.hp-collection.com might be a good starting point to start filling up the gaps which eventually will turn narrower as time goes by... ;-)

I for one keep several copies of the ROM images I've collected, in different places and media. However, I never took the task of classifying them by version nr. (nor by any other concept...) just "dropped them into the bag".

The easiest method I can think of to check out differences between ROM images is an HEX editor. WinHEX.exe is the one I use.

I'm not sure I quite understand the issue you mentioned regarding Card Reader ROM. What sort of "interaction" with the HP-41 may interfere with the ROM extraction process?

Will keep in contact and mail you back with a detailed list of the images I've got as I get back home.




Hi, Diego;

first of all, I think that the NoV32 decided to behave accordingly after some clearing and writing. I erased the RAM by loading NovClr32.HEX at least three times, then I erased the PIC18LF252 (it needed some extra erasure to be considered cleaned by ICProg Blank check...), then I loaded HEPAX plus David Assembler with Labels by using the last update you offered at www.clonix41.org instead of the one you sent me. I loaded the module with NoV32-H0.HEX and it behave as a dummy module,i.e., CAT 2 showed nothing after plugging it in three HP41 (one halfnut, two coconut). Is that OK?

I´ll try loading the card reader 1G image today later after having the NoV32 behaving accordingly. What I did before updating the NoV32 as it is now was:

- load NoV32 with HEPAX and David Assembler (was unstable);

- separate page B from HEPAX chain (following HEPAX manual instructions: BFE7, BFE8 and AFE8 = 000, etc...)

- copy card reder ROM to page B with COPYROM;

At this point the HP41 behaves erratically and I had to remove the NoV32 and write a program to copy the card reader image from page B to page E or F. Then:

- configure MLDL2000 with one SRAM address at page E (or F), or any other one that is not in use by NoV32 mapping;

- plug both NoV32 and MLDL2000;

- copy the card reader image from page B (NoV32) to page E (MLDL2000);

- connect the MLDL2000 to the computer and download the card reader image.

I think RAM2ROM.HEX allows copying NoV32 nonvolatile RAM contents to the computer without the need of such maneuver, but I have never used it. Is that what it is for? Sorry to ask, it came to my mind right now.

The erratic behavior of the Hp41 was mainly activating ALPHA mode instead of ALPHA entry after [XEQ][ALPHA] after the card reader image was copied. I simply could not enter any key with [XEQ _ ] in the display, but I could erase it character by character with the backarrow instead of clearing the hole LCD contents. Also, after executing the program to copy the card reader image from page B to page E, I found it in SRAM 63 of the MLDL2000. I pointed page E to SRAM 00 by programing the MLDL2000, and it ended up in SRAM 63... The program I wrote was:

LBL 00
I simply pressed [R/S] and saw no error message until it finished itself. Please, if there is an easier, safer way to transfer the card reader image to the computer, let me know.


Luiz (Brazil)

Edited: 19 Nov 2009, 1:17 p.m.


Hi Luiz,

I have both a cardreader 1D and 1E and thus the ROM images you want ;)

I have experienced the same issue. Problem is that when coying the CR rom to a lower page, the entry points become active, and this calls for strange behavior. My setup is a bit different, as I have an external MLDL2000 (my breadboard setup) and can combine a physical CR with the MLDL2000, and copying works, until you have both images active.

I copied the CR image from page E to page B, using the MOVE routine in M2K ROM. Note that the SRAM page you need in B can be mapped but disabled (so it can not be read by the '41, but still accepts WROM's).

I will transfer the images to your computer in a few minutes ...



Forgot to mention: keep in mind that the CR code is very hardcoded to page E, and any active CR image in another page than E will cause very strange behavior ....



Hey, Meindert; dankje!

I actually thought of building a kind of port extender (just connectors and cable) so I could connect MLDL2000 into port 3 and do exactly what you mention: set a disable SRAM page prior to copy it. Then I would just transfer it to the computer and copy it back to MLDL2000 in a FLASH position. I´d keep both copies in the computer and in the MLDL2000.

Thanks for clarifying about the weird behavior. I considered that if the card reader could only be placed in port #4, why not to write its code already hardwired? I am not sure about this, but in this case, even internal jumps could point to physical, actual positions instead of relative addressed. I do not know if, in this case, the mcode is simpler or smaller.

Thank you very much, both for the explanation and for the ROM images... 8^)


Luiz (Brazil)


I haven't checked this for sure but I'd assume that the card reader code is indeed had-wired to page E. Any MCODE programmmer will do that to save space and achieve faster response from the system, and HP had the best MCODErs for sure :)

As per obtaining the CardReader image, I did it using COPYROM in the HEPAX, of course. Although this wouldn't work if your HEPAX emulation isn't functional?


Edited: 20 Nov 2009, 1:14 a.m.


Hi, Ángel;

thank you for your follow-up.

I have the NoV32 working fine so far and I'll give it a shot this weekend. We are having some issues in my town because of a possible meningitis surge. At least three fatal victims so far, two of them being students at the univerity I teach in. All teachers were called for some meetings in order to define actions, but this weekend will be a little more easy, I guess.


Luiz (Brazil)

Edited: 20 Nov 2009, 5:56 p.m.


Hi again,

Good to know you got your NoV-32 operative again. :-)

Regarding RAM2ROM it's certainly intended to dump ROM images from any RAM page into a NoVRAM (or the upper 16k in a NoV-32) to a .ROM file in your PC.

The details can be found here.

This utility was considered somehow "experimental" so it never was properly documented, anyhow, if it shows to be useful I'll add some detailed procedures in the next update.

Hope this helps.


PS: Please note, the related .HEX file referred to as RAM2ROM.HEX in the thread above was later renamed to RAM2ROM1.HEX in the update archive.

Edited: 21 Nov 2009, 5:41 p.m.


Hey, Diego; ¡muchas gracias!

I was searching for this very piece of info! Did not cross my mind having it as a post at the archives...

You see, in such cases when an image has been successfuly copied into any NoVRAM RAM page and disturbs calculator operation (like the Card Reader ROM), RAM2ROM seems to be the only way to copy such image to the computer.

Thanks again!

Luiz (Brazil)

Edited: 21 Nov 2009, 9:22 p.m.


Do not forget that M2kM will read the resulting HEX file (and save it a ROM or MOD)



The ROM pacs listing from M. Wehrli at www.hp-collection.com might be a good starting point to start filling up the gaps which eventually will turn narrower as time goes by... ;-)

There is also an online version of this listing:
HP-41 Module Database

Might be a good place for ROM images, too!



Hi Juergen, your on-line DB is an excellent place to get this done. Do you have the capability to also store the images there? If so, this can be the answer to Luiz' request.

I also have dozens of images lying around in different directories across several computers (some of them quite rare)... and wouldn't mind getting them all tidily stored once and for all. Should compile a list during the week-end...


Edited: 20 Nov 2009, 2:33 p.m. after one or more responses were posted


Hi Ángel;

this would really be great! I am not sure if the images I was able to collect would not be amongst the ones you have. In any case, I´ll save a copy of the ones I find amongst the actual modules I have with me and list them here, too. A few weeks ago I bought two 82242A (IR module) and their ROM versions are the same of the other IR module I already have: three IR modules, same ROM version in all of them...

In time: I downloaded a small MCODE from TOS that allows copying ROM images stored in any of the four different banks. Is there any other resource that allows such copies?


Luiz (Brazil)



just to second Ángel´s words: if it is possible to save ROM images, even if there are no direct links for them instead of a regular directory list, that would be great.

And congratulations! The data base is really impressive.


Luiz (Brazil)

Edited: 20 Nov 2009, 8:05 a.m.


I already thought about storing pictures there. Technically this should not be a problem, but time-wise I have to delay these project to end of December. I'm just too busy now. Angel already has my mail address. Contact me and we can work out the details.





I don't see Luiz preocupation with copyright, i have been writing roms for years all copyrighted to me but always give them away for free because there is no money in this endevor, we just crazy love it! Thus free unless money involved.

Edited: 7 Dec 2009, 7:42 a.m.


Hi, Doug;

thanks again for your thoughts! I also believe that after 30 years, being worried about copyrights over a 30YO development is almost (if not total) nonsense. Anyway, who knows what goes on someone else's mind...

My worries go to the possibility of someone tells that this or that ROM images should not be publicly available and then take legal actions. Not that it would be harmful, only boring... and time wasting.

And, o'course, I also crazy love the HP41 and related stuff!


Luiz (Brazil)


I did not start this thread. Dave?
Also, have you noticed Warrens contribution to .rom docs?
It is pretty grand plan to document 41c.

Edited: 7 Dec 2009, 11:51 p.m.


Hi, Doug;

I started this post some days ago, and now it is in the archives, so it has been broken. Never mind. And yep, W. Furlow has written very good stuff, indeed.

My idea is just to locate and put together all possible/available ROM images from HP41 modules and allow them to be downloaded freely (that´s why I was concerned about copyrights). A timeline may arise from this, and also many research material. Although it is a 35 YO technology, it still has its many possibilities. Ángel Martin rewrote his own 4K-wide 41Z a couple of months ago and added many extra functionalities plus an improved 4-level complex stack. Now we count on a new 8K-wide 41Z ROM image. I still have one idea or two about MCoded ROM modules, but I need to study a bit more so I can show some results prior to ask for help too soon.

If we only could bag all HP41's known and publicly available ROM's I believe we'd actually bag a hole chapter in technology history.


Luiz (Brazil)

Edited: 8 Dec 2009, 1:10 a.m.

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