How was this PPC-ROM made?


This e-bay auction has a PPC-ROM that has a paper label on it. Was this one created with some sort of programmable rom module? Here is the photo of it...

Or is it just that the original label was lost and replaced with the current paper one? I guess I could ask the seller, but I figured if there was some way to make these modules that someone here would tell me.


See my question previously:

Here is one knowledgable reply I got:
the module that You show on the hpmuseum page is an EPROM module, I think made by CMT (described in one of the last PPC journals) with 8KB, so two pages fit into it. For example, CCD Version B modules were made from the same EPROM modules, or the SKWID INK Barcode Module.

I think someone copied the PPC ROM into a package as described above.


How do you make a module for the HP-41?

Hear are some thoughts/history. Please correct my mistakes ...

I think someone copied the PPC ROM into a package as described above.

That I know of there were four ways to copy an HP-41 ROM and actually use that copy on an HP-41:

1. Copy it into HEPAX RAM. The HEPAX (HEwlett PAckard eXpansion module) contained 8K or 16K RAM and a ROM that allowed copying a RO<M into its RAM. The RAM is volatile (lost when module is unplugged from calculator, but not cleared by MEMORY LOST on HP-41). The existance of this possibility is not real useful ... the HEPAX is relativrely rare and the last one on ebay exceeded $500

2. A RAM or EPROM Box. Much bigger than a module, but it works, some vintage ones exist, and some smart hobbyists are still making their own.

3. Zengrange ROMs. One-time programmable using a fusible link ROM. New, everything is "1" inside it, once you "burn" a "0" it remains a zero (open-circuit for that bit) forever. There was a low-voltage burner that could plug into a port on the HP-41, and with a ZENROM or CCD module, you could make your own ROM.

4. UV-EPROMs. These were programmable with some king of EPROM burner, and offered the ability to make multiple copies of ROMs. The good news is they can be erased with an ultraviolet light. It requires a significant amount of hardware to program them. I hope to learn more. EPROM modules, I think were made by CMT (described in one of the last PPC journals) with 8KB, so two pages fit into it. For example, CCD Version B modules were made from the same EPROM modules, or the SKWID INK Barcode Module."

I am not aware of anyone producing items 2, 3 or 4.

Best Wishes,

Chris Catotti


Although it could be an EPROM copy, I think it is a regular module that has been labeled. I had an original PPC ROM package a few years ago that I am pretty sure had a couple of paper labels with the module. Another possibility was the orignal housing was damaged and the owner placed it in another one.

I have seen PPC modules with the name stamped or silkscreened on the module.

Another possibility was this was from the first lot of modules. When you ordered your 5000 modules, HP would send out the first 100 or so for final approval before packaging the whole lot.



This PPC module was "saved" from a box of scrap over 10 or more years ago when I worked for HP. I guess it was possible (when the 41 stuff was still being made there) to some how copy rom modules provided you had access to the actual hardware used to make them and ROM burners as some engineers probably did.

I really did not even consider wheather it was a copy or not as I just thought that was what PPC modules looked like.



If You can pull out the handle, it is a HP made module,
if the handle is fixed, it is an EPROM module. The EPROM modules have a small "slot" on both sides, in one You can see the contacts of the EPROM chip. And the side label field on the EPROM modules is smaller than on HP made modules. This is for US made EPROM modules only, the ones made from Zengrange in the UK are different (EPROMs too, but other housing)


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