HP Forums

It's nice to present this project - Building a HP35 scientific calculator clone with a Z80 cpu from scratch.



But without using emulators, HP microcode etc. I have always wanted to rewrite original algorithms, created by David S. Cochran.
As the original HP35 was built 50 years ago, this is a good time to do the same :-)

Everything (hardware, software, source code, working gerbers etc) is on my github page:

https://github.com/olekgr/HP-35_Z80

I hope this project will be interesting for someone.

Very nice! Thanks for sharing your code too!

Great job, especially using the original algorithms !! Does your hp35 even exhibit the ln 2.02 bug ? :-)

Roland

Great work !
So you programmed the whole simulator under Z80 assembly language 8-)
(8 bits)
Looking at your schematic , it is quite inspiring too.

That's impressive, thanks for sharing!

My first reflex would be indeed to use an FPGA, but it's not as fun as using the real Z80 and logic ICs. I used to love this CPU assembly language!

Wow. Great work.
Love the assembly - reminds me of the coding I did as young.

Thank you for sharing!

Very nice! I also built an HP-25 replica using a Z80 but I run the HP microcode in a C emulator. Your software is much more impressive.

My project: https://github.com/eshazen/retro-25