HP-35/45 Simulator for PDP-8

Kyle Owen kylevowen at gmail.com
Sun Sep 4 23:39:52 CDT 2016

Just thought I'd share with you all one of my pet projects for the past few
years. I have written an HP-35 and HP-45 simulator for the PDP-8, which
uses the original microcode from these calculators. Thus, it is just as
accurate as the original calculators, I would believe.

Not really sure why I decided to do this, but I suppose I enjoy both HP
calculators and PDP-8 programming. I guess it's nice to have a scientific
calculator at one's disposal too while sitting in front of a PDP-8, too. It
also shows that something like this could've existed back in the early
1970s if one were so inclined to do it. Perhaps it's also a bit of homage
to the Expensive Desk Calculator for the TX-0 and PDP-1.

Anyways, you can grab the code from here:

The HP-45 support is new as of the past couple of days; I went ahead and
through in a help function to explain the keys. Toggle between 4XXX and
0XXX on the switch register to toggle between HP-45 and HP-35 modes,
respectively. Feel free to give feedback; I've tested it fairly extensively
in SimH with no major issues other than no error indication on the HP-35. I
have a debug mode which prints each register every instruction cycle, but I
haven't used it too much in recent times; I went ahead and IFDEF'ed it as
it also reads from the switch register.

OS/8 support will come soon, as that shouldn't be challenging. You need 8k
to run this, though I also uploaded my original hp35pdp8.pal code which
runs in 4k. It lacks the help function (and obviously the HP-45 simulator),
but otherwise, works pretty much the same.

Big thanks to Eric Smith for his 'nonpareil' work which inspired much of
the simulator.


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