ERAMCO RSU RAMBox - Battery Replacement


I have a 64K ERAMCO RAMBox that I picked up about 10 years ago. Actually, I had picked up two of them (a 32K and the 64K), but the Lithium battery died on the 32K unit and the OS went poof, it evaporated. I remember copying the OS from the 64K unit onto cassette or disk, and sending the unit to a guy in Houston to have the Lithium battery replaced. I was able to figure out how to get the OS back into the unit after it was done, but it took me awhile and a lot of reading. After a move in 2001, I fell out of the HP-41 community, but am now just starting to get back into it, but have forgotten most of what I learned from back then. Some day, mabye soon, I am going to have to replace the Lithium backup battery again, and am dreading having to go back and figure out everything I did to backup and reload the OS. Does anyone have steps they have compiled to do just that?

BTW, I have an Advanced HEPAX, as well as ZEPROMS and a ZEPROM programmer, I can't remember if I needed any of this stuff to reload the OS, or not.

On a slightly separate note, I have not read all of the million or so forum posts since 2001, but it appears that the functionality of these amazing devices has been replicated since then, and potentially available for purchase? What new stuff is available? It would be pretty cool to have a functionally identical ERAMCO Rambox built with flash (no backup power required) that fit into a single module! Does such a thing exist now?

Thanks for any help,

Dan Grelinger


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Thank you for your reply.

No, unfortunately I do not have an HP-IL/PC card. (Or a computer that could use it; I remember that an old 4.77 MHz IBM or clone was needed.) I do have an HP-9114B, and I thought there was a utility (LIF to DOS?) to convert a file for use in the HP-IL drive from a PC.

No, I have no EPROM box, just the ZEPROMS and burner, HEPAX, and ERAMCO Rambox.

I really don't think I need the OS files (yet), since the battery is still good in the Rambox, and the OS is still there from the last time I replaced it. I've either still got the original copy I made, or I could make another, I would only need to figure out the commands again to archive a ROM to storage, using one of the devices that I already have. From my memory 10 years ago, I thought the challenge may have been getting the ERAMCO set up to write the OS to the upper 8K of each 32K bank, since those blocks were normally protected from overwriting so the OS would not be overwritten. Or perhaps the protection existed only in the RSU software? That's something I cannot remember....

Concerning the Clonix, where do I find out what that is? Is it essentially the same functionality as an ERAMCO Rambox? I never heard of a 128K Rambox, is that 32K bank-switched 4 ways?

And a last curiosity, where there different versions of the RSU software? I think mine says 1A and 2A during Cat 2. If there were any updates, it would seem best to use those.




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Do the switches on your 128K version control the writing function to the banks were the OS is? That would seem to make the OS vulnerable to being overwritten. The switches on my 64K version write protect the other 3 8k banks, and also perform bank switching.

Yes, I did get an Eramco RSU manual with my unit. Did you ever find a copy?

I think my ZEPROMS are 16K, but I don't know for sure. I burned one or two about 10 years ago, and I think I remember them being bank-switchable.

Does Diego have a web-site that describes the Clonix? I assume the 24K of ROM is EEPROM (like flash), correct? Is the RAM battery backed-up?

Was the 128K version of the RSU produced by ERAMCO, or was it a mod?


Dan Grelinger


Does Diego have a web-site that describes the Clonix?

Clonix41 Official Site




Add an MLDL2000 to your Christmas list. See for more info. The current batch is sold out, but I am working on a new version. It has both FLASH and SRAM.



BTW - I understand that there you have no more empty card reader shells, but will the MLDLv2 still fit into a card reader shell if one were to empty one/provide one?






Yes, that is true, it will all fit in a cardreaderhousing. For existing users, only the USB print needs to be replaced, the rest can remain the same. One new feature of the MLDL2000 cannot be used, and that is the possibility to do tracing of the HP41 interface, and seeing exactly what mcode the HP41 has been executing. Far that a new print with the CPLD is also required because I do not have enough signals.

There will however be another solution, with a flat box and a short cable under the HP41. But also in that case a module housing and module connector must be sacrificed.

I am now finishing the software release, and will then start prototyping the new MLDL2000.



Great Meindert, thanks for your kind answer. I think it would be kind of cool to trace, so maybe I should opt for the flat box (I think I have a few spare module houses...) Or maybe I should get two - one in a card-reader one in a flat box? ;-)



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