HP-35 origonal 17 prototype?


I supposedly have one of the original 17 lab prototypes HP-35 calculators that I acquired from Tom Holden when he left HP back in the late 1980's. It came with an extra printed circuit board with the letters "B-211 -22 2323" on the top and "00035-60010" on the bottom. Does any one know how to decode these numbers? The story he told me was that the keyboard died on him so he replaced it with a newer keyboard and upgraded the printed circuit board to get rid of the 'bugs.' The 'extra' board was the original. Any help would be greatly appreciated.


00035-60010 is the HP part number of the printed circuit board assembly. The bare circuit board would have an 00035-800xx suffix, but they aren't always marked on the boards. The "B-..." number is probably a designation assigned by the fab house, for their own internal tracking purposes, and there's no real way to decode it without knowledge which fab house was used and what their specific codes were.

What I want to know is the part numbers on the chips, especially the ROMs (round metal cans). They're most likely 1818-xxxx and 1820-xxxx part numbers, though other designations might sometimes be used.


The largest chip is on a ceramic package with a square metal lid 'AMi 7223KPH 1820-0849.' The next chip is marked 'AMi 7219KXP 1820-0848.' The next smaller chip is a plastic DIP marked 'hp 0855 1931-B' The round chip cans are labeled 'AMi K72238BC 1818-0017' 'AMi K7223AT 1818-0020' and 'AMi K7220C 1818-0006.' Man those numbers are HARD to read! Hope this helps.


The round chip cans are the ROMs and both their date codes and HP id number indicate a very early firmware version - bugs all included.

Patrick would you like to lend us the board to read the microcode ?


I would be willing to explore this idea. How would it be done? Where and how would it happen? And finally who are you and how do i know i will get my origional back? My understanding is that this board is VERY valuable. thanks, patrick earhart.


Thanks, Patrick, for considering to help in conserving HP microcode. To answer your questions, I will contact you
directly under your email address, since these matters are unlikely to be of interest to a public forum, except for
the following public announcement:

a major technical breakthrough the last few days (!) has enabled me to construct a HP microcode reader that is able to handle all the Classic series ROMs and does not need desoldering of the ROMs, so the risk of damage is virtually nil.

Anyone willing to lend HP classic CPU boards to our microcode extraction / preservation project please contact me on my email.



Good news about the microcode reader. What approach
did you take? Do traces need to be cut? Is there,
or will there be, a web site that contains the extracted
code (and, ideally, details about the reader)?

Please keep this forum updated on the project---I
think it would be of direct interest to many
readers here.

I'm certainly willing to send you what versions I have:
HP-35 v2 and v3, HP-45, and HP-80. I doubt that
these are in any way unique or rare, though, so
I'll send you the ROM markings first---you can
check if they're duplicates of boards you already
have access to.

Peter Monta


The current HP microcode reader emulates an ACT or CTC and generates "HP word cycles" by software running on an old 100 Mhz PC which I keep in my lab. Advantage: no delay loops needed, it is already slow enough ;-)

The software is written in C and debugged under Linux, then transported and recompiled on the DOS box.

The current hardware options are twofold:

For Woodstocks / Classics, desolder the ROM chips and plug one each into a simple circuit providing power and level translators.

For Classics, desolder just the CTC and hook the reader to a few CTC pads and by microhooks, to a few holes on the main board. The mainboard itself provides the -12V/+6V power and the clock signal level translation.

The disadvantage is: some desoldering needed. But with professional tools and some skills, absolutely no traces need to be cut (I would never do such damage to any of my HPs) and after the chips are resoldered and in place again, and the board cleaned from flux residues, we still have a perfect HP mainboard without any damages.

For the Classics, desoldering the 16 pin ROM ceramic packages or the 10 pin TO cans proved to be too risky, so I reengineered the approach to desolder just the CTC. In the unlikely event that the CTC is damaged during the soldering process (i.e. heat and mechanical stress), a replacement CTC can be salvaged from lowly HP35s or 45s.

For Spice, I still don't have written any reader software. And I still lack a HP27 to see which logic / clock levels would be needed for these early NMOS HP chips.

This is work under progress. I have no doubt it will be of great benefit to the HP user community and schematics and software will be made available to the public domain in due time. First, I must have absolute confidence that the approaches and techniques chosen are sound and foolproof.

Volunteers may contact me under the email given above.



One of my prototype PCBs has no part# at all; the other two have part# "00035-60005"
I think 60010 is "production quality" and not a prototype part, due to the early datecode (my prototype is about 7 weeks earlier) this is probably a V1 board.

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