HP 42S Memory Upgrade


Just got back my calculator after having memory upgraded. Works fine. One thought for anyone else thinking about this upgrade -- if it takes as long for you to enter programs as it does me, it took about 6 hours to enter the 6k programs I had in machine -- imagine how long it will take to enter 30k worth of programs.

Speaking of programs for 42S, does anyone know of a good source for HP 42S specific programs? I know there are plenty of HP 41 programs, but adapting them for 42S so as to take advantage of 42S features is not trivial.

Personally, I would love to have a 42S with lots of memory that could transfer programs to/from PC. I know that 48 and 49 series allow this, but I like small size of 42S.


My 42s is also upgraded and works like a champ.

I don't know of a place for HP-42S specific programs. Sorry. There are lots of HP-41 programs here on the museum, and lots at my calculator site:


The HPX Journal available on CD rom from Jake Schwartz has a few HP-42S programs in the last couple of issues.

There's also a graphical mine hunt game for it too.

Anything else?



Hello, Tom;

about the time to load programs in the HP42S+ (32KRAM) you're right: keystroke sequences may only be abbreviated if you
1) assign and use functions with the CUSTOM menu or
20 create subroutines/subprograms to perform common tasks, what also saves keystroke sequences.

I once wrote a big, big program for the HP42S in 1990, right after it was available in Brazil. The program - a Load Flow basic, standard and accelerated Newton-Raphson convergency method - was for academical purposes and it serve me well: my only top 10 (or A) ever while at the university (Electrical Engineering). Also, that was the first time a student solved the problem automatically with a pocket calculator. I had the program almost finished in my HP41CX, basic memory with program steps and contorl variables, X-Memory with the bus and voltage matrices.

I rewrote almost everything so the new program could deal with indexed matrices instead of X-registers and use internaly available complex numbers resources. The program was even more understandable. I remember I could only work with 10 buses in the HP41, but I gained a lot of extra memory with the HP42S. I did not test to know how "far" it could go in teh HP42S. And at that time, it was an 8KRAM model.

I remember I tested how deep could it be a matrix in the HP42S+ and I thought about writing a program to create a random maximum complex matrix and invert it.

As mentioned by one of our contributors in the first months of 2002, the biggest deal is not loading the HP42S+ with a lot of programs, instead using the extra memory to manipulate larger databases. If you have a standard 8KRAM HP42S and use half of it with programs, then you have about 4KRAM to store data. With a 32KRAM unit you increase extra space seven times, form 4KRAM to 28KRAM. Wow!

Unfotunately my 32KRAM unit stopped working this very evening. I'll open it tomorrow to see what's going on... This unit is the one I used to create the Load Flow program and I bought it in October 1989. What a pitty! But I will try to repair it.

Just a bit of story...

Luiz C. Vieira - Brazil



Looks like your 42s may be sad, at her sisters depart. Other than that, you know you can count on me if she needs parts.



Hello, Renato;

thank you for your support. May I call you today later? (I mean "today" as "Thursday") Please, send me an e-mail with your contact phone numbers. As I mentioned in some posts before this one, I lost almost all of my e-mails and the one that I had your phone numbers is lost.

Thank you again.

Best regards.

Luiz C. Vieira - Brazil


There's plenty on Gene's site- and the ufl in the minehunt game is very useful outside of it. I hope to extend it to a full alphabet at some point.

I'm (STILL) working on a text editor, in my spare time. which isn't so spare, and the program needs some few very serious tweaks beforte it can be called usable.

I really should have something distributable at some point.

After that I have two things I'd like to see. both of which I may have to do myself.

one is a basic clock with alarms or elapsed time computations.

the second (and more fun) is a FPS graphical reworking of the old dungeon game gene has listing for.


Hi, Christof;

I've been looking at the HP42S earlier inner guts and the new HP17BII; also, a few months ago, one of our contributors posted a photo of the earlier HP17BII.

You know what? Internals are the same for the HP42S and the HP17BII. Not even an extra Xtal or IC for clock control/generation. This makes me think that the HP17BII's clock is completely SW emulated. The contributor (was it Paul Brogger?) that posted the photo was sad, as I was, because the HP42S could be still in production as the HP17BII was. Same applies to all Voyagers, as posted in one thread a few months ago, too...

The hard parts are:

1 - finding (if existing) a valid memory position/address where clock counting is updated
2 - reading it so it can be used in a program

The HP28S has a SYSEVAL address that gives the internal 32-bits (or less?) clock counter so you can generate a clock, a stopwatch and even an actual calendar. All of them "working" when the calculator is OFF, of course. I do not know if the HP28S system is able to wake itself up as a result of a past-due alarm while the calculator is OFF, as it happens with the HP48/49/17/19.

That would help a lot. I have no idea if this sort of SW resources are available, but displaying a real-time clock in an HP42S may not be too hard if clock counter can be "seen".

My thoughts and support.

Luiz C. Vieira - Brazil


Hi Luiz,

Don't forget this article: http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=266 for a few tidbits about the clock.

For your sick 42S - check for cracked solder connections on the ram chip, especially pins 14 and 15, the most common failures.


I wrote a posting about stop watch abilities on the HP42S at http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv009.cgi?read=23708 some time ago. In opposite to my old posting I must say, that there isn't or I didn't found any ability to call SysRPL/Assembler routines from the FOCAL code. The operating system area with it's RPL/Assembler code is completely different from the FOCAL area. The FOCAL area is just handled as RAM-WORD object by the OS.

From my actual point of view there may be two possible solutions:

1) Add a "language" ROM and use the XFCN command to expand the FOCAL command set.

2) Replace the HP42S OS by putting CPU controller into EPROM Mode and use the "language" ROM place for a modified OS.




No matter what, this is going to be a bit hackish sinc eI can't extend the 42S any. (right now, anyway)

I've been using registers 40 through 49 for the program itself, I'm wondering if I shouldn't make part of the code require a SIZE 120 or something and use more indirection?

Will people be using a lot of code that will conflict with my registers?

(for memory pointers, just the memo functions will take up somewhere around 600bytes. the full text editing system including file concatenation, a faked directory structure, and such may take as much as 2k- though probably less.)

Two other thoughts I've had involve structuring the memory.

I can use individual matrices per 'text file' and a master matrix to keep a 'directory'

or I can reinvent LIF on the 42S and make one large matrix with an internal directory structure to find the text files, all of which will be included in it. This takes longer but will look cleaner when doing things outside of the text editor.

- one of the reasons this is taking so long is I keep playing with differnet methods like this.

I've also given up on the GETKEY based input system. many people hate the 32Sii alpha keyboard anyway, and I don't have any reasonable system for holding keyboard templates down on a 42S.

I may try that method again later, but it will eat memory and cpu cycles like candy... (no problem for me at 32K ram, but not everyone has that)

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