Two months ago I purchased Christoph Klug’s HPIL/PC card and Jean-Francois Garnier's emu41 to use in resurrecting and preserving the ROM's I had saved to EPROM and/or cassette tape during the early '80s. These highly professional and top quality tools performed flawlessly and now several of the resurrected ROM images and scanned manuals are available on "that other site" for all to download, learn from, and enjoy. Permission to make these images public was graciously granted by my good friend and “partner in crime” ;-), microcode guru Nelson F. Crowle (Prototech). Hopefully I’ll be making several other unique images available in the near future, including the one we successfully used to 'beat the casino's' at the game of 21 - see Nelson's write-up on http://www.hamfon.com/blackjack/blackjack.htm.


Do you know if that downloaded ROM images (*.ROM files) may be recorded again into EPROM ICs?
If so, do you know how to do this?
Best regards


It should be possible. What you need to do first is work out how the 10 bit HP41 words are packed into bytes of the file. Sometimes the file lenght gives a clue here. If it's 8192 bytes for each 4K ROM block then it's almost certainly 2 bytes for each word (8 bits in one byte, 2 bits in the other, and a look with a hex editor will tell you which way round they are!). If it's 5120 bytes for each 4K block, then it's probably packed 4 words into 5 bytes (4 bytes containing the low 8 bits of each word, 1 byte containing the 4 2-bit high bit fields). The latter is more common in my experience, and I've got a program (C, for linux) to extract the data from the files saved by the Eramco MLDL-OS system.

When you've got the data out, you then probably need to split it into high and low bytes, and repack the high bytes (of which only the 2 LSBs are significant) into the format your EPROM box expects (this may well be packing 4 of 2-bit fields into a byte). Then send to an EPROM programmer (may have to convert to Intel-hex first, it depends on your programmer) and burn the EPROMs.

I've done it from files on an HP41 LIF-format disk, but I have no idea if the .ROM files you're talking about are the same format.


I believe it is possible, as Tony has outlined, although I've not tried it. Just off hand I'd think the best and easiest method would be to program the images to a CLONIX plug-in module (see http://www.iespana.es/clonix-41/). The images on "the other site" are in .MOD format. Using the module configuration tool (also available on "that other site") one can easily create the necessary HEX file to program the CLONIX. Once in the CLONIX the images can either be used "as is" (in a handy plug-in module) or subsequently burned to an EPROM using an HPIL EPROM programmer.


Dear Bill,

thanks a lot for transfering / saving this nice rom-image pages "to the other side" and to the future world of HP41 system.

Actual some people are working on different HP41 plug in module solutions (Angel, Raymond). And in parallel we get new hardware solutions like Clonix and MLDL2000 (Diego, Meindert). EMU41 (Jean-Francois)is a helpfully gateway tool to bring this new technologies together...

Regards - Christoph Klug


Bill, this is a beautiful way to complete the "41-puzzle"; your contributions to this community are sensational (starting with the AECROM), thanks very much indeed!

Some of the rescued modules are widely marvelous. Nelson's productions were quite something, really pushing the envelop and loaded with innovation... when I grow up I'd like to program like him!



Hi Bill, great job. We all hope to see more of these things coming our way. BTW, I just had a closer look at the AECROM brochure and noticed a photograph of a young good looking :-) guy at his desk with a calculator. That wouldn't be you 20 years ago, would you?



Hi Miki, No, regretfully that good looking guy in the brochure isn't me. Rather, the picture is of one of my identical twin son's. The good looks (of all my 4 children) come from their mother.

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