trying to work with Zenrom, Novram and Advantage together


Hello, I have the Zenrom, Novram with Hepax and PPCROM flashed and advantage modules. I want to use them together, but no combination in the hp41 ports seem to make them work all. Sometimes advantage is not recognised and sometimes the zenrom displays strange chrs when I make a catalog 2. Is there any way they work together?
Thank you very much


Hi, Fulcrum;

first, consider that HEPAX emulated by NoVRAM tries to allocate itself in the first, lower-numbered, available page (HEPAX documentation calls these 'blocks' instead of 'pages'). As each page is also switcheable into four banks, HEPAX uses the four banks in the lower available page; as each page addresses up to four banks, 4KBytes each bank, HEPAX is actually a 16KByte-ROM module. It might be good idea to also check how is the NoVRAM RAM addressed.

I am not sure about ZenROM, maybe it goes to the lower page related to the port it is plugged in. And the Advantage occupies two banks in the lower page plus one bank in the upper page of the port it is plugged in.

So, consider that only the NoVRAM is plugged in and you want to know which page is the PPCROM addressed. You can use HEXEDIT and test for each of the known page addresses. If yours is an HP41, plug only the NoVRAM and try this:

[XEQ][ALPHA]HEXEDIT[ALPHA]  [ADR:_ _ _ _      ]
5000 [ENTER]
If the HEPAX is actually allocated to page #5, you'll see
briefly in the LCD and the input message [ADR:_ _ _ _ ] back to the display. Now you can try other addresses in the range 8000 to F000 so you can find which page is the PPC ROM allocated to. To try another address once you are already navigating in one page, press the back-arrow (correction) key and key another address in. To exit HEXEDIT, press back-arrow key in the [ADR: _ _ _ _ ] display.

Once you key in a valid address, you can navigate with [SST] and [TAN] keys, being [TAN] equivalent to BST. The regular HEXEDIT display is:

[XXXX YYY _ _ _  ]
where XXXX is the current address, YYY represents its contents (000 to 3FF) and _ _ _ is the input-cue reminder. If you see nothing but 000 in YYY field as you navigate through the page contents, this means the page is empty, i.e., no modules addressed to it. After finding where is the PPCROM image allocated to, you'll be able to plug the other modules accordingly. My suggestion is: plug the NoVRAM in the lower port (prot #1), locate the PPCROM image, turn the calculator OFF, plug the other modules in, one at a time, locate where are they allocated, and see if there is no conflict. I'd suggest Advantage in port three and ZENROM in port four. This would give port 2 free for HEPAX RAM pages. In any way, Diego is the guy to tell you how it is organized.

I saw that in a halfnut HP41CV, HEPAX in NoVRAM occupies port #5, and in a halfnut HP41CX it goes to port #6 (port #5 in the HP41CX is internally used by X-Functions/Time Module).

Not so much of a help to solve the problem, but I guess it will help you going ahead.


Luiz (Brazil)

Edited: 22 Jan 2006, 3:18 p.m.


Thank you very much Luiz


Hi there,

Thanks Luiz, for your detailed explanation regarding page allocation "seeking". I certainly wouldn't have done it better. ;-))

Fulcrum, the main trouble with the configuration you've chosen is that there is not enough addressable space into 41's memory area for that number of modules.

Let's see:

HEPAX ROM is not a trouble as it will fit itself into page #5 (41C or CV) or page #6 (41CX), but HEPAX RAM is, as it will go from pages #8 thru #B. Therefore, you have just 4 free addressabe pages (#C - #F) but a 5 pages modules count: PCC (2 pages, into NoVRAM flash), Advantage PAC (2 pages, don't care about Bank-Switching) and ZenROM PAC(1 page)... Oops, one page too many!

Don't pannic, as usual NoVRAM (HEPAX) allows a nice workaround ;-)

- Just plug in your NoVRAM (port-1) along with ZenROM PAC (port 3 or 4 depending on where your PCC image is addressed to).

- Clear HAPAX RAM from page #B.

- [COPYROM] from wherever your ZenROM is, to page #B. Now you have a copy of ZenROM into NoVRAM's non volatile RAM wich you may handle as if it was ROM.

- Remove ZenROM pac and replace with Advantage.

Now you have them all running into your HP-41!!

Hope this helps.

Best regards.


Edited: 23 Jan 2006, 7:35 a.m.


Hello, Diego, thank you for your help, I am rather new to this hepax and memory structure of the 41, could you explain me how do I do the ram clearing and how could I find the zenrom location?
Thank you


Zenrom module is allocated to the upper page of whatever port it is plugged into. So if you plug it into port say 1, Zenrom will be at page #9 (port 2 - Page #B, 3 - #D, 4 - #F). As per Zengrage "... the reason for this, is to accommodate the growing number of users who are installing modules inside their 41s. Because ZENROM is addressed to the upper 4k of a port, both ZENROM and another standard 4k module can be effectively plugged in to the same port..."

I would plug Zenrom into port 4, COPYROM from #F to #B and replace Zenrom with Advantage, as Diego suggested.


ok and how do I put the address of b anf f pages in the x and y registers?
Thank you


Hi again, I managed to copy the 15 (F) on the 11 B and now it works, still 1304 registers free, how is that possible, I thought it would use 4k and I have the same amount of registers free than before.
Thank you



First a recomendation, it is important to read the HEPAX manual top to toe... :-)

Now for the details:

I'll suppose you've placed PCC images into pages #C and #D.

- Execute [HEPAX 002] to get a "Memory map".

- Clearing RAM is performed by HEPAX [CLRAM] function, you must enter "OK" into alpha register and place the number of the page (in decimal) into X register. It will be advisable to rebuild your HEPAX Filesystem completely, mostly because of the ill configurations you've been using (placing overlapped pages of ROM/RAM) which more likely have left garbage into NoVRAM RAM. So repeat the clearing procedure for every page from #B to #8. (Order is "somehow" relevant)

- Once your page #B (d'11) is cleared, then place source page d'15 (if you plug Zenrom into port 4) in X register, then destination page d'11 into X register, (source page nr. will be pushed to Y register by doing so), then [COPYROM]

- Switch OFF, replace Zenrom module with Advantage and ON again...

You're done!!

Now your register count [HEPROOM] shoud be ok.

Best regards.



Hi, Fulcrum;

If you allow me a suggestion, mainly based on Diego's wise words, it's time to order a MoHPC DVD/CD Set, unless you already have them. All necessary manuals/books to master these modules (or most of them) are already there. A few others may also be found at TOS.

Please, consider this a suggestion. As I mentioned before, I think all contributors in here agree with me when I say it's a pleasure to help when I (we) can. Anyway, sometimes it is a good idea to have such reference/study material in hands so you can go ahead with 'interactive' experiments + knowledge base.

Cheers and success.

Luiz (Brazil)


Hello again mates:
First of all thank you for your help.
I have some sets of documentation, including Hepax, synthetic programming, extend your hp41, etc, they are overwhelming to me as I am starting and I am not used to manage this machines as a "hardcore user", so I am trying to do my best learning, the more I learn the more find this machine amazing, specially in such an old piece of equipment...
See you



Just to keep suggestions 'up to date' (as you mentioned correctly, the HP41 is yet an amazing computational tool), one of the most interesting books I read (been reading, in fact) is "HP41 MCode for Beginners". It delves into the HP41 HW and MCODE structures, as a an 'in deep' complement to HEPAX Manual Vol. 2. You see, dealing with HP41 inner secrets demands knowing some tricks, if I can say so.

I myself am also new in the HP41 'insides', although I use it since the 80's. After I got the chance to put my hands in an MLDL2000 and both NoVRAM/NoV32 in the end of 2005, I started delving into the same secrets you are dealing with right now. I guess I know the feeling of wanting to go ahead and finding a bunch of documents to be understood. Based on all of what I've been reading so far, these documents are somehow compact, and sometimes I wish they have a few more pages to explain some details I know that were not mentioned.

Cheers and success.

Luiz (Brazil)

Edited: 24 Jan 2006, 12:44 p.m.

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