HEPAX - from the treasure chest

[SteenPetersen]

OK - you are really finding some nuggets ;-)

I am happy that you are able to recover the material I have kept for so many years - I will try to provide some insights as far as I remember.

When comparing HEPAX 1A with 1B, then the only differences I spot in the list are the last four functions - 1 through 4. I do not remember what these are used for, but are likely some kind of test functions - if you disassemble them you may be able to tell.

I think the TEST images are the very first code I made to test the four bank switching. We had a couple of challenges - the first challenge was how to test the bank switching in the EPROM part of our prototype breadboard. We could not do this from a RAM program - it had to be from EPROM code. So I wrote some code which I think were the TEST images. The question is then how do we burn the EPROM from this? I wrote another program which converted the images to EPROM addresses and the corresponding byte value per location - in the correct format required to be stored in the EPROM. I ran this program and printed out the EPROM addresses/bytes on the HP-41 printer (you may be able to find this program somewhere on one of the disks as well). We then visited one of our suppliers which had an EPROM programmer with a hex keyboard and one line display. I spent the best part of an hour and manually entered the EPROM content in the programmer and then we burned the EPROM. Finally we stuck it into the breadboard and it worked! - we were able to run ROMTEST to check it out. If it had not worked, then as you can see there were many steps where this could have gone wrong...

On TOULMATH I was helping Eric to create an image of the code he created - I did that a couple of times. It looks like you found those images. Thank you for the link to the french magazines including JPC - I found an article I wrote back in 1985 (http://www.jeffcalc.hp41.eu/divers/files/jpc-25.pdf - on page 30) about a proposal for Machine Language bar code - take a look. This article explains two functions in the BOOT ROM - namely MCP and MCSCAN - have fun ;-)

The ARBEJD (WORK) appears to be a work in progress image - I would be curious to see what you find in this. NYBOOT (NEWBOOT) looks like an updated version of the BOOT image - maybe the same just stored in a 640 register file.

Another fun fact - when working on all the functions we wanted to add to the HEPAX module, then we had more than the 64 functions than you could have in a single module - as also mentioned in the manual. So this is how both the XF/XFA multi-functions as well as the HEPAX/HEPAXA multi-functions came about.

Regards,
Steen